The Cessna 337 operated in the Vietnam conflict. So would suit a Vietnam map if it was ever made.
The King Air is a good choice too and is used by the Royal Australian Air Force as a navigational trainer.
I would support civilian aircraft as long as they didn't divert DCS away from being a combat simulator first and foremost. It would be fun to fly an aerobatic aircraft like the Edge 540, Cap 232 or Yak-54.