Honestly they need to bring back the non-battling content and really firm it up. I’m thinking of the contests from gen 3 and 4. There should be a complete contest quest line and it should be on an importance par with the Beat-gyms-and-E4 quest. I liked SVs three separate quest lines, but two of them were directly about battling and the third was about the Let’s Go battles which just aren’t that interesting.

I want the national dex to be back, mega evolution and all. More difficulty would also be welcome.

I feel like they botched open world in Violet/Scarlet. What they really need is some kind of difficulty options, like level scaling. I’ve done some hacking and it’s honestly really easy to make a toggle so that enemies are scaled to near your party and bosses slightly higher, or not at all if ‘progressing’/grinding exp is important to you.
Some interactions with wild pokemon that aren’t just murder, catch, or die to. Arceus experimented with this a bit in that you could feed them or accidentally wake them up, but I feel it could go further, like aiding one being attacked by another pokemon.