I disagree. Allow a single Gym to have triple battles, and another to have Rotation battles. It challenges especially anyone challenging that Gym and provides a unique experience. It should be pre-determined which one TYPE would be best for each format and mandate that Gym use it.
Gym Leaders, technically, can be promoted to Elite Four (
it's happened before), and we might have to do a graduating format. Have an initial tournament between the various "leaders" and their Gym teams; the best ones get to Elite Four status. The Champion can start out as the winner of the tournament, and that winner can have a team including a wider mix - but ONLY the Champion. There can also be NO Champion to start, and the first to conquer the Elite Four assumes the role; anyone else coming in can dethrone the Champion. The question is whether the Champion would move down, or can the Elite Four ever challenge the Champion with a non-typed team and the winner move up? The entire idea of Gym Leaders moving up and down is the thing I can't wrap my head around as, since Gym Leaders usually live in their towns, I can't see one leaving and then returning a week later after being demoted again. That would be silly. Gym Leaders can perhaps be allowed to challenge once every three or four months, and a defeated Elite Four member assume leadership of the Gym (same type or different); any losing "leader" in such a battle remains a Gym Leader.
I don't know why this is exciting me; I'm not even into the competitive thing. But if I were to serve as a leader and not necessarily challenge the entire league myself, that might be sufficient for me as it would give me the chance to meet the most challengers (and I am not the best battler). My only issue is my nearly full 3DS friend list; I'll have to axe people to take part.
And then there's another question: level restrictions. If every Gym Leader is Lv.100 or all battles are set to Lv.50, it takes away the aspect of being better than the Gym Leader at the outset. Also, if participants can change their team for each Leader, then every Leader is virtually doomed to failure. I presume participants will use the same team throughout the challenge and start with a new team if they want to change?