It seems entirely unlikely to me than Mnuchin would commit a crime in destroying records to cover up for Trump's lawyer's side deals. He can't do it himself, he would have to go through people in his organization who know he is acting outside of procedure and could very well leak that fact. So what is so compelling about these transactions that would make him want to do that? He would effectively be trying to protect Cohen and not Trump, so what interest would he have in going to jail for that guy? Even if it was a request from Trump, would you do that if you were in his shoes?