IG-88 is propotioned differently than a human, and I beleive is a fair bit taller. So he wouldn't work as a player model.

And that leaves the fact that players would be transforming into droids when they pick up a certain kit... IG-88 dies, then another soldier running along picks up the kit and becomes IG-88? If 2142 even has the player model changing into something else in it, I forgot if it does or not. And adding it to normal kit load outs is really out of the question all together.

"Munchkin: One who, on being told that this is a game about politics and intrigue in 17th century Italy, asks to play a ninja."
— Andrew Rilstone