Dempsey as a modern fighter-

I'm sticking with the OP's title, and assuming that, by "fighting," he meant fighting as in boxing. For whatever it's worth, I think Jack Dempsey, coming up in modern times, would be competing where the most money could be made, and, in general, we all know what Weight Division that is. I would say the same for Rocky Marciano and many other Heavyweights from the past.

 

Maybe he could have done so when he was young. But I doubt that he could have done it in his prime. There’s not many good weigh-in photos from his career, especially where he’s flexing. But I’ve seen a couple of good stills from some of his fights though.

There’s a few good ones from the Willard fight, where he officially weighed in at 187 pounds.

I have a hard time seeing where he could have stripped away almost another 20 pounds in order to make SMW.

https://images.app.goo.gl/zkNYDNJN53iYNxhK6

 

REALISTICALLY, I think Jack could have been a Cruiserweight today, but he'd certainly make more money at Heavyweight. And that's exactly where he'd be before long, IMHO. I really don't see the big guys scaring him off, based on the career he had. As for being a Light Heavyweight (175), or Super Middleweight (168), Jack was actually fighting at 200 pounds as early as 1918, before he even won the Heavyweight Title. He was 187 pounds for Willard, probably as low as he could effectively get himself and still feel healthy, by design, for maximum speed. I just do not see him at 168 or even 175.

 

I do think it would have been possible. But I don’t think that he could easily have done it over a prolonged period.

You don’t know that it would have been very very easy for him.

You have no way of knowing that.

You’ve showed me a photo of Caleb Plant to try and prove your point. You’ve chosen Plant because he’s of similar height and reach. But everybody has different body compositions. Different bone density etc. Plant used to weigh-in as a MW when he was younger. But look at someone like Beterbiev who’s thick set. He’s smaller in terms of height and reach than Plant. Yet he doesn’t fight at SMW, and we don’t know if he could have made MW.

Everybody is different. Dimitri Bivol has spoken of fighting at SMW. But he hasn’t of yet. Chad Dawson fought there briefly, but he couldn’t get back for the fight with Andre Ward, where he had an absolute nightmare. It’s easy saying that it’s only 12 pounds. Joe Calzaghe was a career SMW but he had to starve himself in order to make weight. It was extremely hard for him. And when he moved up to LHW, he was weighing in under the limit, where he’d have been no more than 180 pounds in the ring. And he had a walking around weight between 190-200 pounds.

Unless most of Dempsey’s recorded weights are incorrect, I think it’s more probable that a guy who was comfortable between 185-195 pounds who was thick set and looked solid with a low percentage of body fat, would probably have fought at LHW today.