If he decided to not attend, he could stream his response on another venue. Lots of them out there.
Run it at the same time. It would probably get a larger viewership. Have ads and give the money to the Vets.
Even if the moderators try to rip him to shreds in his absence (which is a real chicken s*** move the audience would see through), I think he would easily recover in the days afterward, just by being his old charming, hard-hitting, take-no-nonsense self.
But I like your idea a lot, too! He’s going to come out on top, I’m sure. When they got in the ring with Donald Trump, they chose to play way outside their league.