I think we are talking about playing the strategy part offline with a website showing the map and player's holdings, and the battles online. I already participated in a campaign set up like that, and it was fine except we had to have a complicated numeric system to account for not being able to field partial units from previous battles. Lots of diplomatic negotiating went on with the other players via email or in the foyer, and this was the best part of the game. Diplomacy was at least as important as battlefield skill if not more so. When all the moves were in for the current turn, we played out any battles online. I think it was about one turn per 5 days or so, but it wasn't the only thing players were doing because we still played just battles online as we do now. Playing battles in the context of a campaign that you had put lots of effort into put an edge on them which isn't there in casual games. Also, if someone had to drop out of the campaign, there were other players willing to step in and take over, and you could have battlefield generals conduct the battles for you if you just wanted to play the strategic part, although I don't think anyone did that in the campaign I was in.