Maybe some more vehicles/vehicle options.
Like for the jeep, you could have the option to have a gun mounted on the back instead of all the sitting locations.
I think water vehicles are needed, like boats and especially a submarine. Submarine is one of the vehicles I always thought would be cool for RTB.
I dunno if this is possible but could you make it so you can walk while in a vehicle? So for a plane or something you could move to each seat to sit down instead of just hitting ','.