A plausible scenario, but I think that if the fight is going down tomorrow, I would go with Carnera based on his body of work.
I think one issue here is how good one thinks Firpo was. Some seem to equate him with Baer, as they were around the same size and were punchers. But Firpo's resume is very thin. He was really a top man for only about two years, from the Brennan fight to the second Weinert fight. His biggest win was over an ancient Willard. I don't think he is in Baer's class. Carnera was a well below average champion, but he was much more proven than Firpo.