You can't recast Luke. He isn't Batman or James Bond. He's Mark Hamil, who has now played Luke at different ages. To have somebody else play him in some inserted time period is something that would not work in the long run.
Everybody stans Stan for it-- but it's a fantasy idea. Sure, they could get him to do it, but would people REALLY accept that? Or would you just be dangerously dividing the fanbase again?
Sure, they could deep fake young Mark's face on there, and do an entire series-- and it wouldn't work. It wouldn't feel right. This is a fan dream that sounds great, but I think