Bob Fitzsimmons gets all the comfort s of modern training, fit to fight in the 1990 s. He brings with him that freakish power. Now put him in with Benn, Eubank, Collins, etc fighting at 168lb .
With the caveat of "who knows?".... certain attributes are translatable to any era, power, timing and chin being at the forefront. Bob had those in spades. He is a top ten all time great pound for pound. Were I forced to make a prediction, I would predict that he would waste all those guys. And he would have no problem getting down to 160 either.
I agree, I think his power alone would have the supermiddle s and down ( and up possibly)wary of getting in to the ring with him.
I remember a video of Don Dunphy calling a Bob foster title bout from the garden and him saying old timers told him Foster reminds them of how Fitzsimmons used to fight. Bob had speed, condition, murderous power and was tough as nails.
When Bob Fitzsimmons weighed in at 150 1/2 pounds ringside against Jack Dempsey to win the world middleweight crown, that was DAY OF weigh-in, which means that in today's era, with day-before weigh-ins, he could win world titles at 147, 154, 160, 168, and 175. He'd even have a real chance to win at 200, and particularly so in the era when cruiser was 190. His power carried up well, as seen in his fights with Choynski, Maher, Corbett, Ruhlin, Sharkey, and others. And he could do it at any age. Dude was a freak of nature. Concussive knockout power combined with skill and ring generalship. He knew where, when, and how to hit guys with knockout force, at any weight. That ability translates to any era.
With the range of weight classes and titles that you have to work with today, its hard to imagine him not having success.