from my point of view:
idea is nice.. but..
mimic is not very easy and needs quite some work (1. modelling good enough 2.animation 3. somewhat many skins with low poly models)
if mimic is possible at all on the current models, anything more than talking or laughing would be barely visible(just think of the general level of detail and usual distance between camera<-> player's face.
i agree with further animations like bow,!jump!,dance,forge something,sleep,(drink, and smoke - very important for dwarfs;) ) etc ( some characters still need some work on basic animations.. humans just walk like thy have a broom in their butt...

)
if some know where to get a blender-usable version of the modells., tell me and i'll try to add some stuff (no mimic).
if you want a character moving its mouth while "speaking" it should be fairly easy to do, all you need would be a talk animation ( or 2 where the char open its mouth) and a small pice of code on the client side to play the animation with a certain speed. animation is given by the letters. simmilar to the way HL handels it, works fine with audio's volume used to open the mouth

.
a few nice extra animations to live up the place are nice (like dancing or laying around) but anything beyond this is a lot of work and after all thats what the /me command is for^^
just my 2cents