I have to agree with the air combat system. The old one was in my opinion better. The new version of the combat system is a little bit like in the original x-com, but that doesn't mean it should be the first choice. I would prefere to use the Xenonauts 1 system, because the game felt much deeper.
About the base system: It feels kind of weird to have only one Mainbase fore the hole planet earth. The smaler one only for the aicrafts feel like thats something is missing there. I would prefer to have the choice of building more bases, maybe one or two just for building Aircrafts there or for research/engineering.
With one fixed base it feels kind of unnatural and heavily controlled and not as complex as the old one X1.