I would like a multiplayer campaign. Not going to happen, but I can hope, can't I?

The campaign map from Rome would not work very well, since the player could move, fight, then move armies again all before ending the turn. The map would have to work like Medieval, with all moves planned, then actually occurring during the end turn phase.

Combat would need to be pause-free (even with player v AI matches). The combat phase would be the most troublesome, since it would take the longest to do and the non-involved players would need to be entertained somehow while it goes on (maybe spectator cameras, hell, maybe allow them control of the AI units). If possible, the game should handle multiple battles at a time to speed this up, as long as there wasn't a common player.

TBS games work with multiplayer. Games like MoO2 and 3 and BotF worked fairly well, the only difference would be the possibly epic combat phases which these other games didn't really have.

Regarding connection speed, you could always play with friends on a LAN. It's better that way anyway, you can rag on the slow players and trashtalk during fights. But this is probably too much of a niche market.