Seeing the maps ut4_dealey_b2,ut4_blackhawk, and ut4_intercity got me to think about a map with vehicles.
Other that ground vehicles, I was think about putting helicopters in it...
Though, If I could get them to move from place to place might be great for gameplay-kinda...but, the moving helicopter on ut4_blackhawk had its gliches with moving...though, then again- how fast it moves might have something to do with it.
Idea for "SPECIAL" helicopter: make a model of the helicopter (see attachments), passenger compartment with opening doors- also player spawn area. Attach a MR. SENTRY at front of craft. Look into the ability to fire unguided rockets-or modifed hk69 40mm shoots-from the rocket pods mounted on the wings <- Might run into problems there.
The mounter MR.SENTRY seems like the only probable way to give the helicopter offensive capability.
Though- rockets would be COOL...and would be obvious over kill.