I’ve thought about a similar mod, and I think the single greatest thing to make a game like this work would be the driving/fighting mechanic (drive-by’s).
We’ve all seen regular infantry type gameplay, but never a decent car versus car gameplay mechanic. The closest is something like Battlefield games, but military vehicles are too powerful versus infantry and can be killed easily by the plethora of explosive devices.
I envision 4 players in a car that can shoot through their windows, in a car that can’t be killed easily. The car players would have the same firepower as on foot, but with the mobility of the vehicle. This would not simply dominate other infantry players, but change tactics. Taking out any explosives other than maybe molotav cocktails would help cars live longer, and hopefully make them more of a fighting vehicle rather than a kamikazee machine or for transport and then dumped ala Battlefield.
One gametype I thought of was Drive By. Team A attacks using cars while Team B must stand around an inner city type house completely surrounded by streets. You can only go on the porch of the house, but not in it, and one Team B player is the ‘leader’ that Team A must kill. The leader cannot ever totally hide since the house is surrounded by streets, and Team A must perform driveby’s and kill the leader, while Team B protects him.
Another gametype, Hoods is just like GTA’s missions where you must capture all the hoods. This could easily be made into a Battlefield type conquest gametype, with different cars available in different hoods.