[Resike]

If you call this after you created a frame, then the frame is gonna be scaleable, and it's gonna build up everything needed for it:

function PowaAurasOptions:ResizeFrame(frame)
    local Width = frame:GetWidth()
    local Height = frame:GetHeight()
    local resizeframe = CreateFrame("Frame", nil, frame)
    resizeframe:SetPoint("BottomRight", frame, "BottomRight", - 8, 7)
    resizeframe:SetWidth(16)
    resizeframe:SetHeight(16)
    resizeframe:SetFrameLevel(frame:GetFrameLevel() + 7)
    resizeframe:EnableMouse(true)
    local resizetexture = resizeframe:CreateTexture(nil, "Artwork")
    resizetexture:SetPoint("TopLeft", resizeframe, "TopLeft", 0, 0)
    resizetexture:SetWidth(16)
    resizetexture:SetHeight(16)
    resizetexture:SetTexture("Interface\\ChatFrame\\UI-ChatIM-SizeGrabber-Up")
    frame:SetMaxResize(Width * 1.5, Height * 1.5)
    frame:SetMinResize(Width / 1.5, Height / 1.5)
    frame:SetResizable(true)
    resizeframe:SetScript("OnEnter", function(self)
        resizetexture:SetTexture("Interface\\ChatFrame\\UI-ChatIM-SizeGrabber-Highlight")
    end)
    resizeframe:SetScript("OnLeave", function(self)
        resizetexture:SetTexture("Interface\\ChatFrame\\UI-ChatIM-SizeGrabber-Up")
    end)
    resizeframe:SetScript("OnMouseDown", function(self, button)
        if button == "RightButton" then
            frame:SetWidth(Width)
            frame:SetHeight(Height)
        else
            resizetexture:SetTexture("Interface\\ChatFrame\\UI-ChatIM-SizeGrabber-Down")
            frame:StartSizing("Right")
        end
    end)
    resizeframe:SetScript("OnMouseUp", function(self, button)
        local x, y = GetCursorPosition()
        local fx = self:GetLeft() * self:GetEffectiveScale()
        local fy = self:GetBottom() * self:GetEffectiveScale()
        if x >= fx and x <= (fx + self:GetWidth()) and y >= fy and y <= (fy + self:GetHeight()) then
            resizetexture:SetTexture("Interface\\ChatFrame\\UI-ChatIM-SizeGrabber-Highlight")
        else
            resizetexture:SetTexture("Interface\\ChatFrame\\UI-ChatIM-SizeGrabber-Up")
        end
        frame:StopMovingOrSizing()
    end)
    local scrollframe = CreateFrame("ScrollFrame", nil, frame)
    scrollframe:SetWidth(Width)
    scrollframe:SetHeight(Height)
    scrollframe:SetPoint("Topleft", frame, "Topleft", 0, 0)
    frame:SetScript("OnSizeChanged", function(self)
        local s = self:GetWidth() / Width
        scrollframe:SetScale(s)
        local childrens = {self:GetChildren()}
        for _, child in ipairs(childrens) do
            if child ~= resizeframe then
                child:SetScale(s)
            end
        end
        self:SetHeight(Height * s)
    end)
end

There are still a few thing to do it with, like change the resize button's texture onmousedown and up.
Also ot exlude or only scale the scale button itself with lower frequency, to prevent it beeing unclickable. But its working properly.

Right click on the resize texture, reset the frame to the original size.