Yes it's possible. Why don't you start with editing existing classes, it's way easier. Do you have the BF2 Mod Tools? If not go to lucasfiles. I'm not 100% sure if I know how to do everything right. I started with BF1 because it's simpler. I was able to edit classes on BF1. Wait, I just looked at my BF2 mod tools. Looks like they have a visual munger in this version. Should be no problem munging sides. How much about modding do you know?
FYI
Munging means compiling
Sides is the directory units and turrets are in.
TROOPERS
Hybrid Mode
