Yeah, you could do that however...
-the vehicle would be able to jump, crouch and strafe.
-there wouldn't be any vehicle physics (build up of speed, turning)
-changing weapons would ruin the "illusion"
-since when can vehicles fit through doors?
-you would have to do a lot of work with sounds, getting rid of footsteps and stuff
If you were a wizard at programming, you could edit the GAME.EXE and add in code that would allow vehicle scripts to be used. If you want vehicles in your game don't bother using FPSC. Learn Programming and use Dark Basic Pro.
Opposing Force