I may have missed this in a patch or so ... but since when isn't it possible to change the font flags of the ChatFrame Tab Text?
I know I had it like this in my old UI and it worked, but now it isn't anymore.
Lua Code:
for i = 1, NUM_CHAT_WINDOWS do
local tabText = _G["ChatFrame"..i.."TabText"]
tabText:SetFont(NAMEPLATE_FONT, 11, 'OUTLINE')
end