This is an idea my friends and I had when playing with some custom-added (via mods) airplanes that had cargo-storage for vehicles:

1.) Creating a larger map for Arma 3 (maybe put Altis and Stratis together and add some smaller isles between them?). Helos would take too long and are too small for carrying all the soldiers and material to another isles.

2.) Adding cargo aircrafts (like AC130 - this was the one of the mod) with large cargo storage. Airplanes would be faster than helos and this way traveling larger distances like from one isle to the other would make helos very slow and unusable compared to the aircrafts.

3.) You now can put vehicles or tanks in the aircraft (getting them in via selection (comparable to when boarding a helo as soldier) screen because afaik the Arma engine is having problems with driving one vehicle into another)

This would integrate another point of simulation to Arma as some people have to play as aircraft-pilots to carry material and soldiers from one island to another. You could also integrate a parachute-drop of vehicles directly into the battlefield.

4.) Additionally the smaller isles could have tunnels or fortresses you can attack by boat or helos.

(I´m sure this is cannot be done with a simple update, but maybe it´s something BIS could integrate in an AddOn or DLC)