How about vehicle mounted weapons? as we now have the passenger seat and vehicle mods in general I think a belt fed M60 in a pickup would be a cool thing. Maybe not the most useful of things but certainly funny.
Could be done for example as a mod like "gunner seat with machinegun" for that sweet visual look of the vehicle or just a "gunner seat" which would be a seat on top of the pickup somewhere and the player sitting there would use their own weapons.
Could be expanded to other vehicles of course that are large enough especially a helicopter if such a thing is ever hopefully added to the game.