MM is not popular enough to pull off the Sakura/Otome-Gumi concept now. They were selling out arena tours back then, and added those smaller venue, split-group gigs as a way to offer fans a more intimate experience. They're doing small-houses now because that's all they can fill. I can't see them releasing separate singles of new material, and without new material, what's the point of splitting up the groups?
Just get the group down to around ten girls and get on with it.
MM can absolutely sell out hall tours still, they're the only group that's guaranteed to do one every fall and spring. They're not doing small 3/400 capacity venues because they can't do anything bigger.