Maybe the galaxy thinks he is dead but I think the ideal would be to have him in self exile. A batman like figure that appears and disappears out of nowhere, helping out around the galaxy as a form of penance. A symbol.
As cheesy as it sounds, this is kind of what I would have wanted. Rey and Ben wouldn’t be hooking up in secret or anything, he’d just become a wandering fighter for justice, trying to right some of his wrongs. Potentially with his mother’s lightsaber.
Obviously there’s no way to make that happen in an edit, but it’s what seems like a feasible story decision to me. He DEFINITELY could not join up with the Resistance and be like “It’s cool, I’m a good guy now!”