I don't play those sidegame things, but it might be interesting if a game had all of them (contests, super contests, pokéathlon, and musicals, yes) - I guess it'd be irritating for the 100% completion people, but it's totally possible for the population of a region to be entertained by more than one non-battle pokémon competition. Still, while there could be a bunch of prizes from such things - it is mastery over an aspect of the games and should be rewarded, probably - I wouldn't put TMs as one of them. Though if contests had something like BP, it could work?
Anyhow, forgot this: There probably should be more double battles, too. Even with the dark grass, the combo moves they introduced this generation don't get used all that often, so it seems like such a waste. Most of them could be optional, as in you'd normally cross two people's lines of sight at once but can talk to one to take them on one at a time. There should be more doubles than triples and rotation, anyway.
Team Plasma seems like it'd be perfect for it, at some points - they talk about how the other grunt will help take you down, in Dragonspiral Tower. That works a lot better if they're meeting you two or three at a time. I don't see them getting too involved in rotation battles because that'd mean sticking to rules, but ganging up on you? Oh yes. This also gives the opportunity to have multiple tag battles alongside your rivals.
Other small things - you can fight Bianca as soon as you beat the Elite Four the first time, or else she has higher-levelled pokémon when you fight her post-second E4 run. Cheren could get a level boost the second time you beat the Elite Four, too.
Getting a legendary early in the game is cheating xD. It will probably be more like an item.
You can get Cobalion and Virizion as soon as you get surf...? Though if that's a response to Grimdour, I interpreted it as getting the stone, at least initially.
I don't particularly like the idea of choosing what world you're in, though. It seems like it should be grey/clear and not stripes/checkers, or something. (Besides, we've already done that, by choosing which game to buy.) Cell Battery Guy would be good for such a thing, sure, but it could be blended together better than just taking bits of both preceding versions. A third world representing Kyurem, where you can have both greenhouses and vegetable patches, without hopping between dimensions.
N getting Kyurem and you having to get both Light and Dark Stones as a reverse of both
Emerald and
Platinum could be interesting, but it is more likely to be the other way around. That puts you as the underdog - one legend against two, and yours is
broken until you manage to unlock Kyurem's new forme - in the same way it did when you're marching to face N, even though you haven't awakened your legendary yet. And it follows the pattern of your version mascot being yours, and connected to you.
