i had an idea for standard "universal" classes, where there are, of course, set weapons and each class had a special ability. some classes have weapon options.
Assault- Primary: Blaster Rifle, Secodary: Pistol, Ability: MedKit
Demolition- Primary: Rocket Launcher, Secondary: Light Repeater, Ability: Mine Layer
Recon- Primary: Sniper Rifle/Carbine, Secondary: Pistol, Ability: Cloak
Engineer- Primary: Shotgun, Secondary: Pistol, Ability: Repair
Scout- Primary: Carbine, Secondary: Pistol/Light Repeater, Ability: Jet Pack
Support- Primary: Heavy Repeater/Flamethrower, Secondary: Pistol, Ability: Ammo Dispenser
Commando- Primary: Carbine, Secondary: Pistol, Ability: DemoCharge
and then you have your unique units for each faction.