Very good ideas, not so sure about the airpad however. I really felt that airpads at towers in PS1 harmed gameplay. The disposable nature of aircraft is something I think many players would rather not see return in PS2. Anything to help prevent that is good in my eyes.
I think it would be fun if deployable structures were modular in some sense, allowing the ability to build more complex facilities or bases in a way; rather than one large, upgradeable structure. If that's possible, I don't know but it may appeal to the arm-chair commanders of strategy games and more players is usually a good thing.