you should not "force" a certain HUD. but if the 3team cgame/ui modules are not capable of loading stock HUD files, then you should modify the modules not to use the stock cg_hudFiles cvar: use, instead, something like cg_hudFiles3Team (defaulting it to "ui/hud.txt"). this automatically warns users that 3team HUD modifications require 3team-specific HUD files, and automatically requires the user's "confirmation" to load a HUD that is not supplied with the 3team mod. (this is what has to be done for 1.1 mods due to a 1.1's client behaviour of propogating cvar values to non-base mods. the described problem would not exist in 1.2, just be sure to use an fs_game other than "" and "base" on the 3team server.)