[Phanx]

However, this likely will not affect Bartender's buttons, because it doesn't just inherit from a font object; it also explicitly sets a font:

	-- adjust hotkey style for better readability
	button.HotKey:SetFont(button.HotKey:GetFont(), 13, "OUTLINE")
	button.HotKey:SetVertexColor(0.75, 0.75, 0.75)

	-- adjust count/stack size
	button.Count:SetFont(button.Count:GetFont(), 16, "OUTLINE")

I use the following code to "fix" the fonts on Bartender buttons:

local LAB = LibStub("LibActionButton-1.0", true)
if LAB then
	-- Bartender4
	LAB.RegisterCallback("FixFonts", "OnButtonCreated", function(_, self)
		--print("OnButtonCreated", self:GetName())
		local scale = self:GetParent():GetScale()
		local hotkey = _G[self:GetName() .. "HotKey"]
		if hotkey then
			local font, size = NumberFontNormal:GetFont()
			hotkey:SetFont(font, size / scale, "OUTLINE")
		end
		local count = _G[self:GetName() .. "Count"]
		if count then
			local font, size = NumberFontNormal:GetFont()
			count:SetFont(font, size / scale, "OUTLINE")
		end
		local macro = _G[self:GetName() .. "Name"]
		if macro then
			local font, size = GameFontHighlight:GetFont()
			macro:SetFont(font, size / scale, "OUTLINE")
		end
	end)
end

My primary aim is to scale down the fonts, because I've scaled up my buttons a lot, but you could easily adjust the SetFont lines to do whatever you want.