I don't know about Regal, I think as a HW he would get crushed.
I know Haku could have beaten Royce Gracie and ended MMA, as their are stories of him being a tough mean SOB that liked to rip guys noses off in bar fights.
Danny Hodge could have been the LW or FW version of Brock Lesnar he was an Olympian level boxer and wrestler and at 70+ I think he could still take 90% of this forum.
and he liked that apple.
Before wrestling was televised and it was a carnival trick they used to have these guys called "hookers" that would just f up the ring patrons.
Kane actually has some solid MMA skills, and you can find a number of Japanese wrestlers that could have transitioned to MMA.
And then you have a number of wrestlers Shelton Benjamin, Curt Hennig, Kurt Angle, Charlie Haas, Dolph Ziggler etc etc etc.
Jack Swagger he was like a 20 time all American. Shawn Michaels sweet chin music, he could take anderson
Yeah I think any of the pro wrestlers that were really good at amateur wrestling might of had a good shot if they had started training right after college or earlier. I think Jack Swagger (real name Jake Hager) could of been pretty good. The guy wrestled at the same time as Cain and IIRC was only a few spots behind him and had to wrestle the guy that won fairly early on. He was also listed as 6'5"-6'6" and 260lb+ as a amateur. Seems like a decently quick and athletic guy for his size too. No clue if he would be any good at striking or submissions but with enough training he might of been and we know he can wrestle. But I think all of those guys are in their 30's and 40's now so I wouldn't expect it to happen and even if it did it might be to late (unless they've been training already).
Oh and Dave Bautista has had one fight last year. But I don't think he had any major experience in other martial arts and he is 44 now.