[MiRai]

The last post I made didn't work. I also tried to copy the entire chunk of code and rename the MirrorTimer parts to TimerTrackerTimer like so:

-- timer tracker!
  lib.gen_timertracker = function(f)
    for _, bar in pairs({'TimerTrackerTimer1','TimerTrackerTimer2','TimerTrackerTimer3','TimerTrackerTimer4','TimerTrackerTimer5'}) do
      for i, region in pairs({_G[bar]:GetRegions()}) do
        if (region.GetTexture and region:GetTexture() == 'SolidTexture') then
          region:Hide()
        end
      end
      _G[bar..'Border']:Hide()
      _G[bar]:SetParent(UIParent)
      _G[bar]:SetScale(1)
      _G[bar]:SetHeight(16)
      _G[bar]:SetWidth(280)
      _G[bar]:SetBackdropColor(.1,.1,.1)
      _G[bar..'Background'] = _G[bar]:CreateTexture(bar..'Background', 'BACKGROUND', _G[bar])
      _G[bar..'Background']:SetTexture(cfg.statusbar_texture)
      _G[bar..'Background']:SetAllPoints(bar)
      _G[bar..'Background']:SetVertexColor(.15,.15,.15,.75)
      _G[bar..'Text']:SetFont(cfg.font, 14, "THINOUTLINE")
      _G[bar..'Text']:ClearAllPoints()
      _G[bar..'Text']:SetPoint('CENTER', TimerTrackerTimer1StatusBar, 0, 1)
      _G[bar..'StatusBar']:SetAllPoints(_G[bar])
      --glowing borders
      local h = CreateFrame("Frame", nil, _G[bar])
      h:SetFrameLevel(0)
      h:SetPoint("TOPLEFT",-5,5)
      h:SetPoint("BOTTOMRIGHT",5,-5)
      lib.gen_backdrop(h)
    end
  end

And then add lib.gen_timertracker(self) right next to where lib.gen_mirrorcb(self) is in core.lua. That didn't work either and broke the target and targettarget frame of oUF_Fail. I recruited someone in an IRC channel who knows ~20% more Lua than I do (not much) and he couldn't figure it out either. He did point me towards a section of Skinner which skins the mirror castbar and battleground countdown timer like so:

function aObj:MirrorTimers()
    if not self.db.profile.MirrorTimers.skin or self.initialized.MirrorTimers then return end
    self.initialized.MirrorTimers = true
 
    self:add2Table(self.uiKeys2, "MirrorTimers")
 
    local objBG, objSB
    for i = 1, MIRRORTIMER_NUMTIMERS do
        objName = "MirrorTimer"..i
        obj = _G[objName]
        objBG = self:getRegion(obj, 1)
        objSB = _G[objName.."StatusBar"]
        self:removeRegions(obj, {3})
        obj:SetHeight(obj:GetHeight() * 1.25)
        self:moveObject{obj=_G[objName.."Text"], y=-2}
        objBG:SetWidth(objBG:GetWidth() * 0.75)
        objSB:SetWidth(objSB:GetWidth() * 0.75)
        if self.db.profile.MirrorTimers.glaze then
            self:glazeStatusBar(objSB, 0, objBG)
        end
    end
 
    -- Battleground/Arena Start Timer (4.1)
    local function skinTT(tT)
 
        -- aObj:Debug("skinTT: [%s, %s]", tT, #tT.timerList)
        for _, timer in pairs(tT.timerList) do
            -- aObj:Debug("skinTT#2: [%s]", timer)
            if not aObj.sbGlazed[timer.bar] then
                local bg = aObj:getRegion(timer.bar, 1)
                _G[timer.bar:GetName().."Border"]:SetTexture(nil) -- animations
                aObj:glazeStatusBar(timer.bar, 0, bg)
                aObj:moveObject{obj=bg, y=2} -- align bars
            end
        end
 
    end
    self:SecureHookScript(TimerTracker, "OnEvent", function(this, event, ...)
        -- self:Debug("TT_OE: [%s, %s]", this, event)
        if event == "START_TIMER" then
            skinTT(this)
        end
    end)
    -- skin existing timers
    skinTT(TimerTracker)
 
end

Looking at that I'm really not sure where to go from there.