My number 1 request is for air transports. I would only implement them with the following guidelines:

Limited carry capacity - 1 tank, 2 jeeps, 4 infantry (regardless of improvement level)
Limited range per turn - about double a jeeps range
Only movable within your boarders - its a transport, not an attack craft

My main purpose for this unit is for rearranging your battlefield quickly. If you are fighting a two-front war, and reach a treaty with one of the parties, it can takes days ( in my case 7) to reallocate those unit. With air transport, it could be accomplished much sooner.

Just my 2 cents.

Or maybe let units attack further over your own land than enemy land, since they're just passing over and not bothered with "claiming" or fighting.

I would really like to see this done!!

How about adding a rail movement option to the units w/ reduced deffense and attack while embarked...this would allow for quick deployment in the rear but u'd still need to disembark for a turn to be at top combat strength ..1/2 strength 1/2 movement on disembarking turn ...something like that....this will allow for interdiction air strikes on embarked units, greater rear echelon movements and orginization but wont allow someone to blitz and entire army to the line then attack right away at full strength...air movement should be limited from air base to air base w/o adding an airbourne troop & maybe an air interdiction mission for jets or CAP ...i could ramble for hours...ha!