Automatically delete leagues with 0 members, or mandate a replacement founder from the existing member list when a founder leaves a group.

Or require a minimum of 5 members prior to the start of the season. Failure to do so could result in termination of the league.

I think that if a league has 1 member, and they leave that league then a message stating that "If you remove yourself from this league, the league and all its money will be deleted" would work just fine.

There shouldn't be a limit to number of members in a league.

I'm with cire as long as that number is above 0. If someone thinks their ensemble has enough influence to single-handedly make a profit on their own league events, all the power to them. There are very few ensembles that could pull that off, and I would guess you would need influence in excess of 40,000 to do that profitably.

Maybe if there are more than 1 leagues in the same class that have less than 5 members ex.(drum line), all the members could merge into one league.