I had a dream sometime - maybe I didn't, but hear me out - which honestly led to an unpopular opinion of mine.
In my dream, there was a game called Pokémon Eclipse taking place in a new region next to Alola. Team Skull was STILL around, but now there were actual Gyms to face instead of the Island Trials. As long as you downloaded a copy of either game, by way of a newly revealed Lock-On "Play Along" command, you could boot up Eclipse and combine both games into SOLARMASS and LUNARMAATTER a la Sonic 3 & Knuckles. Either game by itself would ideally end with your Pokémon team having leveled between 55 and 65, but since SMLM has tightened level curves, the S&M half would have to end shortly after your starter reaches its final evolution, and the Eclipse half would leave off with the average team levels reaching between 75 and 90.