Well, I noticed you were talking about civ2, so hopefully I don't have to explain it to you. Anyways, civ 2 had a multipalyer editon (if you didn't know, couldn't tell) where you could set turn length (unlimited/1/3/5/etc) and each player would take their own turn.
BUT
There was also an option that was, sadly, excluded from the release but someebody added it back in. Anyways, it let all human players "do" their turns at the same time, and then the AI would make separate turns. (AI would never move at the same time). So, maybe do something like this for OPM (players can pick real-time or turn-based for multi)? know that I'm thinking of it, will people be able to set AI players in single/multiplayer games?