So here's some general ideas for Kanto sequels I came up with. Some of them good, most of them bad. Some of my own, some nabbed from this thread
>Takes place some ~10 years after the Gen 7 games
> Same starters, but dex also includes all the new evolutions to Kanto mons, and some mons from other regions, mainly Johto. Also Kanto forms to other Pokemon. Many "tropical" Pokemon have Kanto forms where they are more suited to an urban environment like Kanto - EG: Dark/Grass Tropius.
>Starting town is in one of the Sevii Islands, new professor
>First gym is in the next town in the same island. Gym leader is Lorelei, who also runs the Trainers School.
>Sevii Islands are in the game but they are not as expansive as in FRLG, but definitely more interesting.
>After the first Gym is completed you take a ferry to Pallet City. In the years since Red became Champion and resigned his post, he's sort of become a legendary trainer and people travel to the town where he grew up, which allowed Pallet Town to grow into a major city. Oak's lab is now a museum - implied Oak passed away.
>You meet your rival here. Some cocky rich kid who's the son of Blue's sister, has the starter of the type that's strong against yours but it's the Johto starter - so if you picked Bulbasaur he has Cyndaquil, for example
>Blue pops up here and then - he's a traveling retired trainer who offers sage advice: think Adler's role in BW2
>Lavender Town now has a Ghost Type gym, it's ran by Agatha's grandson
>Most gym leaders are new characters, some towns that had gyms before don't have them anymore and vice versa, like the case for Lavender town.