it'd be absolutely dreadful since ren sans self-control about his more aggressive traits was basically ren while he was a villain, so he'd probably spend half the cycle trying not to be that much of an asshole again...but yes switching the other character is always an option

YEAH ren's fairly public so it'd spread quickly if he was missing, but he's more concerned about bad shit happening to his people while he's gone, so he's kind of holding onto the idea that that it doesn't seem to affect where they came from and hoping there's not some kind of other weird reason for what he's heard from others