Well in v118 there is already support for changing fire modes.
You mean haveing a greneade launcher underslung on an assault rifle, and pressing a certain key to switch between the nade launcher and regular fire. Or being able to to do the same just with switching between fully-auot or semi-auto.
If this is what u mean then yes it is already possible.
Vehicle support can be "faked" already i believe. But larger maps would be a pretty big drain on resources without a huge rewrite of the engine(I think I know next to nothing abou coding)
I recently learned to sleep with my eyes open. ..... God am I tired