A very simple mod. In this mod you build Jumpjet VehicleTypes (Siege Chopper, Floating Disk, Nighthawk, and more!) from airfield. Jumpjet Vehicles (Helicopters) now share the same building queue with pad aircrafts. Roofs of war factories would never open! The engine limitations have been lifted.
I think the harbinger could use a redesign. Change the propellers under it to VTOL like engines and make the weather control device aspects of the plane less huge and bulging and all over the place. Keep it in the middle of the aircraft and not on the wings.