Well thats not going to work, I have tried many things Like
Say If I wan't to be a scientist I would open up the pack file and Scroll
down to scientist, open it, and then Save Model as player.mdl in the Valve/Models folder. Now this apparently worked out good Until the time came that I put in a Camera, When I compiled the map and triggered the camera it would close down half-Life (...Whenever I came into the camera view) So You will probably have to edit or use only the player.mdl files that can be found in only the multiplayer games.
Anyways Someone else???