Each team have 3 slots.

Generally, I use slot 1 for whatever my current team is, slot 3 is all the same across all teams, that's for ranked. And I swap slot 2 for arena/masuri or whatever else when I need something else.

The only problem I have is when one of the summon I need, for whichever team, is not golden (for example, the fox line up uses tonton), so I have to swap it for other purposes for the sake of the stat difference. But other than that, everything is fairly manageable.

To be clear, I'd love it if masuri, arena, ranked and whatever else that might come out have their own summon sets. However, it's not nearly as a big of a problem as you make it out to be with proper management.