A team based combat engineering game.
All the different vehicles and machines would have each their own little quirks. The game would rely on the players skill and knowlegde.
Everything would be complex to operate. For example things like repairing a damaged vehicle would include opening up the thing, locating the problem if not indicated by its dashboard, if available. Do whatever it takes, wehter its tightening a bolt, fixing a hole in a pipe, reconnecting torn cables, or even replacing the whole thing. People would be able to do quick fixes and modifications to their vehicles, but it wouldnt be some fancy drag drop menu, but actually moving around physical objects in the world.
Imagine you are a pilot, returning from a recog mission(some of the other teams guys decided to camp somewhere out in the mountains or something), suddenly the engine shudders and starts loosing power, alot of smoke comes from it, forcing you to do a crash landing. You land somewhere out there in the wild, long away from the much more knowlegdeable team mates back in the hangar. What would you do? I would grab the service kit i was so lucky to stow away, open up the engine and look inside. Oh, look, a piston jammed! Damn how am i going to fix this? *starts meleeing the piston part* oh finally its no longer jammed, a bit battered now.. but ill get that fixed when i get back. Oh jesus that was a hard takeoff! i'd bet the gears are completely fucked! Oh god its getting windy.. HOLY SHIT IM SPINNING OUT OF CONTROL, NONONONONON- *crash* "You are dead."
Later a bunch of guys finds a plane wreck, missing the right wing, later another bunch of guys drives out to get the wreck home. Investigation turns out a very hard bump had loosened a bunch of bolts.
Kind of like Combat Flight Sim meets Ace of Spades with a bigger and smoother map, combined with alot of detailed ways of fixing stuff.. oh god also realistic surgercial procedures! That would be badass! Like saving a bunch of plane crash survivors. Or the joy of shooting down planes with a flak gun, seeing their pilots ragdoll all over a cliff, scattering body parts everywhere! Then salvaging their plane for parts for your car that some random bear decided to fuck up.