Hm, I don‘t know. On one hand it‘d sure be pretty cool battling with the own team on different levels but on the other hand this would mean no fair chances for everyone.
Cuz the ranking list would look the same as in the arenas before boosts were added to the game. Those with lvl 28 teams will of course be up in the list and those who have like hybrid-level teams will stay somewhere deep down in the list.
Like if we‘d get a rare only tournament with different lvls but no boosts. Then I sure won‘t lvl my rares beyond lvl 20 for the victory. But this means, that I basically don‘t even have to participate for too long cuz soon I would face players with rare creatures beyond lvl 26.
So I would be one of the few people that wouldn‘t appreciate a level-based tournament. I sure can imagine how happy the players with high lvled creatures would be.
I still prefer the current system. No boosts and all creatures set on one level, gives equal chances to everyone (except for the speed ties, this really needs to be solved).