Replace aging actors ( i.e.: Harrison Ford ) with a younger actor to resume all of his characters without having to recast those roles. The actor gets to be Han Solo, and Indiana Jones... etc.

Most actors caged in one type of role, definitely wouldn't want to be the "new" version of x famous actor and have to copy their style. On top of that just look at the fans and people on the internet, even if you try you'll never make them happy by trying to take on the roles of a well established actor, comparisons will always be there and even if you're better a lot of people won't see it like that most probably. So yeah no, it would be a disaster in my opinion, nothing good can come from that unless a lot of little things align.