No to any such areas, during and especially out of the game story or after it.
Of course. The game has its specific story to tell. Character arc to present. Specific mechanics and rules of engagement.
Any such "area" would diminish the main campaign and whatever any player did with his characters.
This is really self evident but still, it looks like it has to be said out loud.
A separate mini campaign or a mod, thats fine. Whatever.