[@TheNoCoKid] Nope. No other Gigantamax forms. You can Dynamax any Pokemon though, and even then, Piers was considered pretty strong lore-wise despite the fact he refused to use either one. 

[@Fabricant451] Since gym leaders also fight one another in the Champion's Cup, I've always assumed that the rank they receive every Cup affects where they're based next season. I'm also of the mind that they can also be demoted to the Minor League if they actually do THAT bad or if the Minor League leader has spent a ton of time training in order to promote. So for instance, my character can be 7th this season, but she could have been 8th last season but just did poorly in battle.  I hope that makes sense.