Obviously Ellis isn't beating Joe Louis and wouldn't even be much of a fight for him.. But could Jimmy have beaten a lot of the top contenders and had a presence during the period?
Ellis has a chance.....just don't get tagged by some big hitter below Louis grade. Schmeling, Galento, MBaer. (Louis would always win IMO.)
I'm thinking he would have joined the ranks of other good black heavyweights of that era who never got close to a title shot.
Jimmy was a middle that grew to a Heavy. With eras considered, a late 30's-early 40's Jimmy may not have put on that poundage, and a Jimmy, at that time, may not have possessed the modern technique.
Benny Leonard & Billy Conn & John Henry Lewis easily had modern techniques being they are listed in the Top Ten greats of their respective divisions.
Elliis would not have done well. Louis KOs him easily. Braddock, Baer, Schelming, Conn beat him every time. Jimmy would have beaten some of the second tier heavies of that time.
I doubt he would have done quite as well in the 30s and 40s and he did in his own era. I mean, he was kind of 'fortunate' with his friend Ali bein unable to box for a few years, that gave Ellis an opportunity. Big televised fights for 'world titles'. He was good enough to be ranked in any era though.