I most certainly would enjoy a Pilot/driver branch, I actually was surprised there wasn't any Pilot/Driver in this game when I bought it. The more I have to manage the happier I am, and to me that kind of game is made of ground combat just as much as base/resource/crew management. I guess it varies given anyone's taste but in my mind the success or failure of a ground mission is only the result of good or bad management beforehand, and not the other way around. Moreover, air combat is a huge part of the game, you basically spend your whole game fighting for air superiority and I really think it would add a lot to it if pilots/drivers were implemented.
To me lack of any possible gain of experience for anything else than my soldiers is a bit of a disappointment, or rather, as much as I enjoy the game (oh boy I do), sending planes makes me feel neutral since it doesn't feel like I'm risking anyone's life, and vehicles wells.. I just don't use them at all, I prefer my guys to grab all the xp they can get.