I'd love to see the Hoenn remakes set in a later timeline. If they just kept the previous storyline with only graphic updates and changes in pokemon teams, it could end up being just 'slightly' better.
They could have a new player character. In RSE, there was actually a little brother of the rival, so he could be one. The girl character could move in from some other region. They could make slightly different starting points.
Brendan, May, Wally could be either supporters throughout the game, or postgame bosses at certain places.
Also, it would be good to see changes in gym leader designs. Like, Tate and Liza as a teenager, and Brawly actually having a surfer sprite. Wattson might have to retire by then... but they could just have him sit in an electric wheelchair. Flannery could be more mature and lady-like (similar to the Beauty sprites). Roxanne as a more teacher-ish image. No changes necessary for Winona, Norman or Juan, I guess.
I want to compete with Wallace and Juan in the Contests, too XDD They could be in the Master Ranks randomly. I was disappointed in RSE because of that.
The E4... Sidney is fine as he is. In fact, I'd say he has the best Dark-Type team members. Pheobe needs adjusting - two banettes, two dusclops, and one sabyele? That's mean. Only three kinds of pokemon to use... *sigh*. Drake's Emerald team was much better, but I wish he wouldn't use Shellgon. Glacia also needs more pokemons to use - two sealeos, two glalies, and one walrein...
They should expand the Hoenn dex and include more evolutions. Like, Snorunt is native to Hoenn, so Froslass should be included in the dex, too.
As for Steven, yes, he already plays a huge role in the RSE games, but I wish for MORE action XDD Put him as the champion AND enable the double battle with him at the space center. He should also play a part in advertising his coorporation's stuff more... XDD