I read a lot of the multiplayer related posts and I hope I'm not repeating anything someone has already suggested.  Anyway, here goes.

I think the multiplay function could be a sort of a hybrid between realtime and turn based. 

• Everyone could take turns at the same time.
• Turns would not be required to match up one on one.  Meaning in the time it takes one player to take one turn, another player might have completed three.
• Conflicts, interactions between players and items on the map, and diplomatic interactions between players would take place in real time.

The biggest benefit of this would be that no one would ever have to wait for someone else to finish a turn to continue playing.  It would also create some interesting strategies that would not exist in normal play.  If you decided to build up a huge empire, as it got larger and larger and you had bigger and bigger armies to order about your turns would take longer to complete.  Another player may decide to keep their empire smaller and tighter allowing them to complete two or three turns for every one that you can take.  You would have to balance being big and powerful but heavy and slow with being small, mobile, and quick but with tiny hit and run style armies. 

The problems that some multiplayer schemes have with who gets to attack who or who gets the goodie bag or monster lair first would be easily resolved.  It would literally go to whoever queued up the action first. 

The only odd thing I can see coming from this sort of setup would be that your sovereigns would end up being vastly different ages from one another, as would their kids.  There would have to be some leeway about a 25 year old sion getting married to a 85 year old one and still being able to produce the next generation.