Toney's lateral movement and sneaky counters would trouble Dempsey. They wouldn't be the foil of him. Dempsey showed against Gibbons, who also happens to be the best comparison for this fantasy match, that he can be patient and shorten his leather. For every pop Tony landed he would be forced into an unproductive shell. And every time he felt the urge to follow up his high boxing IQ would be all too aware of the risk. Toney may have even given a prime Holyfield more trouble than Dempsey - Jack routinely sparred with middleweights and was better equipped to 'pin them down' than most heavyweight greats.
I happen to think that being the undisputed heavyweight champion is quite a significant accomplishment. This content is protected I am sorry if you dont see it this way.
James in his prime was incredible. But very inconsistent. How many performances did we really see him at his best? I mean his absolute best? If Nunn, Johnson and Body Snatcher were his best performances then that says more about them than him. That leaves what, Barkley, Jirov , Ruiz and Holyfield? That's my biggest issue with him his peak performances were that rare it makes them anomalous in his career.