Since its hotseat there is no need to schedule sessions and such, just do your turn, save and send the file to the next guy (if for example your army is attacked between someone else's turn by the ai, he saves in the battle message and sends you it, you play the battle and then do the save transfer for whos turn or battle is next.
So everyone can take their time on doing the turns though if everyone is in the same speed it would be best.
While battles between players cant be played in the campaign by both, doing some equivalent battles through hamachi in custom battles might be possible, followed by the deletion on both sides of the numbers lost ( so the battle isnt actually started on campaign, the attacker just gets his army near the other one ). That or auto resolve.
Im not sure im best to organize but if anyone wont and you guys really wanna play i will be up for it. A topic where everyone posts some summaries (or actual AARs) of their turn and roleplaying and etc would keep everyone updated on the campaign. Some 4 or so would be ideal i think, i will do some runs on a quick hotseat campaign on eb 2 2.3 to check if all is good.