I would keep the groups the same OS through DP with them maybe having Brock leave at the end of AG/BF and having it be just Ash and Dawn in DP. For BW, I would definitely have Hilda as the female traveling companion along with Cilan, allowing Iris to be a gym leader and then maybe becoming a Champion. For XY(Z), I would have Serena be either a Sky Trainer, with a competition to go with it, or have her challenge the Battle Chateau to become the true Chateau Queen. If Pokémon Showcases were a requirement, I would have Shauna replace Clemont and Bonnie and do them. If not, then I'd probably keep Clemont and Bonnie. As for Sun and Moon, I would keep the classmates as is, though I would have a bigger focus on Lillie, even after they save Lusamine.