Yeah, I think bareknuckle is a few notches below MMA, even at HW. Look at Roy Nelson. He went 4-12 in his last 16 MMA fights. He didn't even do well in Bellator. But he KO'd one fighter in Gamebred Bareknuckle then went to a split decision with Alan Belcher. He may still have some power, but he's a 47-year old who holds the record for the most significant strikes absorbed without being KO'd. I'm surprised he isn't drinking out of a straw.
And look at Belcher. After an 8 year layoff from MMA, wins 4 BKFC fights in a row then one fight in Gamebread. I think Rothwell is where he needs to be if he wants to win some fights.