It might not be that hard to do. If an agent wants to group his players, he will just have to wait until there is a scrimmage team with all those slots open, then wait for other scrimmage games to play out and for his scrimmage team(s) to play. It could be hours before that happens, but if you really want them to play together that badly, I guess it would be worth the wait.
Bort would have to set up a queue for scrimmage teams. It would probably only be used rarely, so I don't think this is high priority, but it would be interesting for those who want to use it.