[unlimit]

Alrighty, so I got it ALL working except for a few tiny things.

I plan on GREATLY expanding the functionality of my rotation priority feature later on for all of the classes I play, so I wanted to be able to really customize the button skin and such on my feature. I pretty much copied the IconsCustom button system into my feature, except, it doesn't actually work like it should... everything shows up in the descriptor, but - for example - I'm not able to actually set the color of my buttonskin in the options even though it looks like I am, it just remains white on the unitframe.

Also, I am using "Hide Empty Button", just, whenever my icon isn't up (which is whenever I'm not targeting a hostile unit), it still displays the button skin.

Here are my two features, so you get the idea:

function TRUESYS.PriorityHunterBeastMastery()
    local gcd = 1.5
    local level = UnitLevel("player")
    local focus = UnitPower("player")
    local duration, _
 
    if not UnitCanAttack("player", "target") then
        return
    end
 
    -- 1. If your pet is on the target, Kill Command.
    if UnitExists("pet") and UnitHealth("pet") > 1 and IsSpellInRange(RDXSS.GetSpellBookId("Growl", BOOKTYPE_PET),"pet","pettarget") == 1 and focus > 50 then
        _, duration = GetSpellCooldown("Kill Command")
        if duration <= gcd then
            return GetSpellTexture("Kill Command")
        end
    end
 
    -- 2. If the mob is going to live long enough, apply Serpent Sting.
    if focus > 25 then
        if not UnitDebuff("target", "Serpent Sting") then
            _, duration = GetSpellCooldown("Serpent Sting")
            if duration <= gcd then
                return GetSpellTexture("Serpent Sting")
            end
        end
    end
 
    -- 3. If mob is below 20% health, Kill Shot.
    _, duration = GetSpellCooldown("Kill Shot")
    if duration <= gcd and ( UnitHealth("target") / UnitHealthMax("target") < 0.2 ) then
        return GetSpellTexture("Kill Shot")
    end
 
    -- 4. If you will have enough focus to use Kill Command on cooldown, use Arcane Shot
    if focus > 85 then
        return GetSpellTexture("Arcane Shot")
    end
 
    -- 5. Cobra Shot or Steady Shot.
    if level < 81 then
        return GetSpellTexture("Steady Shot")
    else
        return GetSpellTexture("Cobra Shot")
    end
end
 
-- Hunter 4.3 Priorities for CLCinfo (modified for OpenRDX) by Phanx @ [url]http://www.wowinterface.com/forums/showpost.php?p=251728&postcount=2[/url]
function TRUESYS.PriorityHunterSurvival()
    local gcd = 1.5
    local level = UnitLevel("player")
    local focus = UnitPower("player")
    local duration, _
 
    if not UnitCanAttack("player", "target") then
        return
    end
 
    -- 1. If the mob is going to live long enough, apply Serpent Sting.
    if focus > 25 then
        if not UnitDebuff("target", "Serpent Sting") then
            _, duration = GetSpellCooldown("Serpent Sting")
            if duration <= gcd then
                return GetSpellTexture("Serpent Sting")
            end
        end
    end
    
    -- 2. Explosive Shot
    if focus > 50 then
        _, duration = GetSpellCooldown("Explosive Shot")
        if duration <= gcd then
            return GetSpellTexture("Explosive Shot")
        end
    end
 
    -- 3. If mob is below 20% health, Kill Shot.
    _, duration = GetSpellCooldown("Kill Shot")
    if duration <= gcd and ( UnitHealth("target") / UnitHealthMax("target") < 0.2 ) then
        return GetSpellTexture("Kill Shot")
    end
 
    -- 4. If mob will be alive long enough, Black Arrow.
    if level < 61 and focus > 35 then
        _, duration = GetSpellCooldown("Black Arrow")
        if duration <= gcd and ( UnitHealth("target") / dps > 15 ) then
            return GetSpellTexture("Black Arrow")
        end
    end
 
    -- 5. If you will have enough focus to use Explosive Shot and Black Arrow, use Arcane Shot.
    if focus > 85 then
        return GetSpellTexture("Arcane Shot")
    end
 
    -- 6. Cobra Shot or Steady Shot.
    if level < 81 then
        return GetSpellTexture("Steady Shot")
    else
        return GetSpellTexture("Cobra Shot")
    end
end

RDX.RegisterFeature({
    name = "(True) Hunter Priority Icon";
    title = VFLI.i18n("(True) Priority Icon");
    category = VFLI.i18n("Textures");
    test = true;
    IsPossible = function(state)
        if not state:Slot("DesignFrame") then return nil; end
        if not state:Slot("Base") then return nil; end
        return true;
    end;
    ExposeFeature = function(desc, state, errs)
        if not RDXUI.DescriptorCheck(desc, state, errs) then return nil; end
        if desc.owner == "Base" then desc.owner = "decor"; end
        if not desc.usebkd then desc.usebs = true; end
        local flg = true;
        flg = flg and RDXUI.UFFrameCheck_Proto("Frame_", desc, state, errs);
        flg = flg and RDXUI.UFAnchorCheck(desc.anchor, state, errs);
        flg = flg and RDXUI.UFOwnerCheck(desc.owner, state, errs);
        if flg then state:AddSlot("Frame_" .. desc.name); end
        return flg;
    end;
    ApplyFeature = function(desc, state)
        local objname = "Frame_" .. desc.name;
        local usebs = "false"; if desc.usebs then usebs = "true"; end
        local ebs = desc.externalButtonSkin or "bs_default";
        local usebkd = "false"; if desc.usebkd then usebkd = "true"; end
        local bkd = desc.bkd or VFLUI.defaultBackdrop;  
        local os = 0; 
        if desc.usebs then 
            os = desc.ButtonSkinOffset or 0;
        elseif desc.usebkd then
            if desc.bkd and desc.bkd.insets and desc.bkd.insets.left then os = desc.bkd.insets.left or 0; end
        end
        local showgloss = "nil"; if desc.showgloss then showgloss = "true"; end
        local bsdefault = desc.bsdefault or _white;
        local hidebs = "nil"; if desc.hidebs then hidebs = "true"; end
      ------------------ On frame creation
        local createCode = [[       
local btn, owner = nil, ]] .. RDXUI.ResolveFrameReference(desc.owner) .. [[;
if ]] .. usebs .. [[ then 
    btn = VFLUI.SkinButton:new();
    btn:SetButtonSkin("]] .. ebs ..[[", true, true, false, true, true, true, false, true, true, ]] .. showgloss ..[[);
elseif ]] .. usebkd .. [[ then
    btn = VFLUI.AcquireFrame("Button");
    VFLUI.SetBackdrop(btn, ]] .. Serialize(bkd) .. [[);
else
    btn = VFLUI.AcquireFrame("Frame");
end
btn:SetParent(owner);
btn:SetFrameLevel(owner:GetFrameLevel());
btn:SetPoint(]] .. RDXUI.AnchorCodeFromDescriptor(desc.anchor) .. [[);
btn:SetWidth(]] .. desc.w .. [[); btn:SetHeight(]] .. desc.h .. [[);
btn._t = VFLUI.CreateTexture(btn);
btn._t:SetDrawLayer("]] .. (desc.drawLayer or "ARTWORK") .. [[", 2);
btn._t:SetPoint("CENTER", btn, "CENTER");
btn._t:SetWidth(]] .. desc.w .. [[ - ]] .. os .. [[); btn._t:SetHeight(]] .. desc.h .. [[ - ]] .. os .. [[);
btn._t:Show();
btn:Hide();
frame.]] .. objname .. [[ = btn;
]];
        state:Attach(state:Slot("EmitCreate"), true, function(code) code:AppendCode(createCode); end);
 
        ------------------ On frame destruction.
        state:Attach(state:Slot("EmitDestroy"), true, function(code) code:AppendCode([[
VFLUI.ReleaseRegion(frame.]] .. objname .. [[._t); frame.]] .. objname .. [[._t = nil;
frame.]] .. objname .. [[:Destroy(); frame.]] .. objname .. [[ = nil;
]]); end);
        state:Attach(state:Slot("EmitCleanup"), true, function(code) code:AppendCode([[
frame.]] .. objname .. [[:Hide();
]]); end);
 
        ------------------ On paint.
        state:Attach(state:Slot("EmitPaint"), true, function(code) 
        if desc.test then
            code:AppendCode([[
frame.]] .. objname .. [[._t:SetTexture(GetSpellTexture("Kill Command"));
frame.]] .. objname .. [[:Show();
]]);
        else
            code:AppendCode([[
frame.]] .. objname .. [[._t:SetTexture(TRUESYS.PriorityHunterBeastMastery());
frame.]] .. objname .. [[:Show();
]]);
        end
        end);
        return true;
    end;
    UIFromDescriptor = function(desc, parent, state)
        local ui = VFLUI.CompoundFrame:new(parent);
        
        -- Name/width/height
        local ed_name, ed_width, ed_height = RDXUI.GenNameWidthHeightPortion(ui, desc, state);
        
        -- Owner
        local owner = RDXUI.MakeSlotSelectorDropdown(ui, VFLI.i18n("Owner"), state, "Subframe_");
        if desc and desc.owner then owner:SetSelection(desc.owner); end
        
        -- Drawlayer
        local er = VFLUI.EmbedRight(ui, VFLI.i18n("Draw layer"));
        local drawLayer = VFLUI.Dropdown:new(er, RDXUI.DrawLayerDropdownFunction);
        drawLayer:SetWidth(100); drawLayer:Show();
        if desc and desc.drawLayer then drawLayer:SetSelection(desc.drawLayer); else drawLayer:SetSelection("ARTWORK"); end
        er:EmbedChild(drawLayer); er:Show();
        ui:InsertFrame(er);
        
        -- Anchor
        local anchor = RDXUI.UnitFrameAnchorSelector:new(ui); anchor:Show();
        anchor:SetAFArray(RDXUI.ComposeAnchorList(state));
        if desc and desc.anchor then anchor:SetAnchorInfo(desc.anchor); end
        ui:InsertFrame(anchor);
        
        -------------- Display
        ui:InsertFrame(VFLUI.Separator:new(ui, VFLI.i18n("Button Skin parameters")));
        
        local chk_bs = VFLUI.CheckEmbedRight(ui, VFLI.i18n("Use Button Skin"));
        local dd_buttonSkin = VFLUI.Dropdown:new(chk_bs, VFLUI.GetButtonSkinList);
        dd_buttonSkin:SetWidth(150); dd_buttonSkin:Show();
        dd_buttonSkin:SetSelection(desc.externalButtonSkin); 
        if desc and desc.usebs then
            chk_bs:SetChecked(true);
        else
            chk_bs:SetChecked();
        end
        chk_bs:EmbedChild(dd_buttonSkin); chk_bs:Show();
        ui:InsertFrame(chk_bs);
        
        local ed_bs = VFLUI.LabeledEdit:new(ui, 50); ed_bs:Show();
        ed_bs:SetText(VFLI.i18n("Button Skin Size Offset"));
        if desc and desc.ButtonSkinOffset then ed_bs.editBox:SetText(desc.ButtonSkinOffset); end
        ui:InsertFrame(ed_bs);
        
        local chk_showgloss = VFLUI.Checkbox:new(ui); chk_showgloss:Show();
        chk_showgloss:SetText(VFLI.i18n("Button Skin Show Gloss"));
        if desc and desc.showgloss then chk_showgloss:SetChecked(true); else chk_showgloss:SetChecked(); end
        ui:InsertFrame(chk_showgloss);
        
        local color_bsdefault = RDXUI.GenerateColorSwatch(ui, VFLI.i18n("Button Skin default color"));
        if desc and desc.bsdefault then color_bsdefault:SetColor(VFL.explodeRGBA(desc.bsdefault)); end
        
        local chk_bkd = VFLUI.CheckEmbedRight(ui, VFLI.i18n("Use Backdrop"));
        local dd_backdrop = VFLUI.MakeBackdropSelectButton(chk_bkd, desc.bkd);
        dd_backdrop:Show();
        if desc and desc.usebkd then
            chk_bkd:SetChecked(true);
        else
            chk_bkd:SetChecked();
        end
        chk_bkd:EmbedChild(dd_backdrop); chk_bkd:Show();
        ui:InsertFrame(chk_bkd);
        
        local chk_hidebs = VFLUI.Checkbox:new(ui); chk_hidebs:Show();
        chk_hidebs:SetText(VFLI.i18n("Hide empty button"));
        if desc and desc.hidebs then chk_hidebs:SetChecked(true); else chk_hidebs:SetChecked(); end
        ui:InsertFrame(chk_hidebs);
        
        function ui:GetDescriptor()
        local name = ed_name.editBox:GetText();
        local ebs = nil;
        if chk_bs:GetChecked() then ebs = dd_buttonSkin:GetSelection(); end
        return {
            feature = "(True) Hunter Priority Icon", name = name, owner = owner:GetSelection();
            drawLayer = drawLayer:GetSelection();
            w = ed_width:GetSelection();
            h = ed_height:GetSelection();
            anchor = anchor:GetAnchorInfo();
            -- display
            usebs = chk_bs:GetChecked();
            externalButtonSkin = dd_buttonSkin:GetSelection();
            ButtonSkinOffset = VFL.clamp(ed_bs.editBox:GetNumber(), 0, 50);
            showgloss = chk_showgloss:GetChecked();
            bsdefault = color_bsdefault:GetColor();
            usebkd = chk_bkd:GetChecked();
            bkd = dd_backdrop:GetSelectedBackdrop();
            hidebs = chk_hidebs:GetChecked();
        };
        end
        
        return ui;
    end;
    CreateDescriptor = function()
        return {
            feature = "(True) Hunter Priority Icon", name = "bmpi", owner = "decor", drawLayer = "ARTWORK";
            w = 14; h = 14;
            anchor = { lp = "TOPLEFT", af = "Base", rp = "TOPLEFT", dx = 0, dy = 0};
            externalButtonSkin = "bs_default";
            ButtonSkinOffset = 0;
            bkd = VFL.copy(VFLUI.defaultBackdrop);
        };
    end;
});

Honestly, except for the button skin, I'm 100% happy with the outcome of my work on these. They're exactly what I wanted. c.c