>after finally winning a league, he decides to finally come home to spend some much needed time with family and friends (and all his mons that are neeting it up at oak's)
>there, you introduce the new protagonist, a young boy (the age ash was when he started)
>the young boy of course see ash as a god, he's got all those awesome mons and he saw so much of the world and he won a league and all that!
>ash teaches him the ropes
>doing that, he realizes how much he misses adventures, that and how boring pallet really is
>much to everyone else's chagrin, especially the girls, he decides to yet again get back on the road with nothing but his pikachu at his sides
>the young boy, and now protagonist sets out to follow his tracks
there
of course it'd be better if ash actually aged visually, but sadly enough this'll never happen so who gives a shit
and from there you could have the young boy start out with the indigo league, and we could see how much it changed with the years and rediscover most of the secondary characters ash met years prior, or you could have the boy try to 'follow' ash and sail on a boat or whatever into the new region ash went
you could have a rivalry form, where the boy would keep running by the gyms as fast as he can, to try and keep up with ash but of course he couldn't, he doesn't have a lvl 300 pikachu after all
and of course secondary characters and events would slow him down, he'd meet people and pokemon that would follow him on his journey, and finally, he'd meet ash in the league since ash would've become the champion by then
you could have them cross paths every now and then, or you could simply never see ash through the entire thing, and by the end the protagonist (and audience) wouldn't even know if ash is still around, so the surprise reveal would be that much better
yeah, I think that's how I'd do it
