for 3, there would likely need to be a turn limit (in hours or days).  Simultaneous turns would be pretty manditory I'd say.  you could download the previous turn(s) actions at any time, and you'd have to submit your turn actions in the amount of time provided for the turn (say you have 24 hours to submit a turn, you could submit your turn anytime during that 24 hours).   

I vote strongly towards no. 1.   Not just for hotseat games, but also because its fun to play 2 'players' at once, perm alliance style.   I've done that with friends in Advance wars before (we each play 2 COs on a 4 player map).   games that have split screen or hotseat multiplayer should allow it with online play as a general rule.  At least for non-ladder play (games that are unranked in whatever ranking system is available)

I still say that this entire "Everything will be hosted by us and when there's problems or you don't have direct access to us, you're screwed, muahahahahaha, ACHTUNG!"-idea is poppycock! We'll have multiplayer, but not really.

And yeah. Still a dealbreaker. I'd like a definite answer to the issues raised before I finally pre-order. I'm almost kinda glad I haven't, yet.