It doesn't have to be anything too exotic or realistic to begin with. Think of it as a beer-n-pretzels addition to the game. Just make it so you can spawn in the maproom with a rifle instead of the 45, and perhaps .join an M3 or C47 piloted by someone else as a grunt. If airborn, you parachute out like bailing from your aircraft; if in an M3, they driver has to stop to let you out. Provide a few perked weapons, like and SMG or bazooka or panzershrek. A few simple extra movement options, like crouch and prone crawling. Oh, and a satchel charge as standard equipment (deployed like a bomb drop, maybe with a 10 second delay to run away), to take out bunkers/fuel/ammo/radar/etc and to capture the maproom. It'd be a fun distraction, without unbalancing the game overall. Sometimes, if when you're off your game flying-wise, it's fun to have an alternative. Just saying...
