There are a few options we can take. My whole goal would be to keep as many people interested for as long as possible. With that goal in mind here are two Turn ideas, add more if you have them or let me know which one you like/dislike.
xWeeks per turn. So each week people would make their moves on a set day and then have 2-3 weeks to play any games they might have created in their moves.
Open Play - Play games as much as you want, gain territory etc. If this is something people like I will have to adjust the map a bit, but thats ok. usually to keep things at least close you can't play the same person back to back.
Im sure there are other options but these are the two im most familiar with. Thoughts?