I realize I didn't cover every single aspect of what would need to be adjusted for a multiplayer campaign, just my idea for the best way to get certain aspects of a campaign converted. As was mentioned in the other thread, an overlay could replace many town scenes, so the game won't need to be paused, and at most in my games when visiting a town for anything other than a tournament or exploration, I never spent more than a couple minutes before moving on. It'd just pass as regular time, so you'd be spending a day at most in game time.
In regards to simultaneous battles, I'm not sure how the game will work, but since multiple players are involved, couldn't each one player battle be it generated on their own PC, and then after the battle ends upload just the results to the server/host? I don't know anything of programming or coding, but if having simultaneous battles processed by the host was an issue, I don't see why anything other than the end result would matter to the campaign.