Apparently several A-List, big name celebrities have been calling Trump to get on the show to "challenge themselves." Of course, this could just be Trump bragging himself up as he so commonly does.
At any rate, I felt bad for the girls last season. The guys had several A-listers in Gene Simmons, Vincent Pastore (even those who didn't know him by name, knew him as Big *****), and Piers Morgan (due to America's Got Talent being the most watched summer show in the country). Lennox Lewis and Trace Atkins are pretty well known too. The others were at worst B-listers. Baldwin could get his brother to come and help them out, so yeah...even if he is not an A-lister, he at least had connections to them. Their worst celebrity was Tito Ortiz, and Ultimate Fighting has a pretty strong fan base, I believe and at the worst...he is a very respected business man with a lot of knowledge on the subject.
Meanwhile, the biggest celebrity on the girls team was Marilu Henner. It wasn't a fair match up especially since celebrity was such a huge selling point on so many tasks. The teams need to be more evenly balanced this time.
Anyhow, to answer your question, George Foreman would be a great choice, but may have a bit of an unfair advantage as he is so skilled in marketing and runs his own little corporate empire. I'd say maybe target some really well known celebrities who are just past their primes and don't work much anymore. Someone like Chevy Chase for example.