I won’t disagree with your thoughts in the main.
However when I look for someone for the party to insert as the designated loser of stature (no pun intended), Bloomberg seems likely.
I don’t see a billionaire accepting a “designated loser” position. Ego just won’t do it willingly.
This is a last chance for Bernie for anything. Being the nominee would be the greatest achievement he could hope for; losing against Trump would be acceptable (unbeatable and “evil”). He’d be an enthusiastic candidate, a true believer that will be content to take the fall just for opportunity & principle.