Also, Q3 physics are WAY TOO "bouncy" for a fortress style game. To emulate the gameplay of the first TF it is more logical to use more faithful physics to that.
True. Q3 physics are full arcade, TF is more realistic.
Do you know Perfect World ? This is an MMORPG with a great customization feature for characters, particularly the head, and an interesting thing is that to overcome the fact that you can't really see the details in-game, when you click on a character you see its head on the HUD. I think this greatly simulate a dialog.
But most interesting are the customization options, and even if you can't do polymorphic changes due to engine limitation, you maybe can permit some free customization like resize some particularities like eyes, mouth, nose or head ? Or permit transformations like rotations and placement, à la Wii's Miis ? After it's only a matter of some packets transporting coordinates of these elements, and would be downloaded just once at the beginning of the game (or after when dying).