I think he still rethinks his game post-McCall and becomes more cautious. Pre-McCall he was good enough to destroy Rudduck and Bruno and beat Tucker and Mason. He'd still be favourate to beat McCall in the rematch and top Holyfield and Bowe and clean up the division. I also think he still changes trainers. How about he goes to Brendan Ingle's Wincobank gym, that would be fun
Mercer would have been the first solid choice to beat Lewis. He'd have beaten Butler, McCall, Morrison, etc.
I am going to stuck my neck out and say he would not have been as sucesful as he did eventually turn out.. Lennox changed his attitude , gained weight and became a lot bigger stronger and bolder heavyweight... I think he would have taken on Morrison as he was always muted to , looked good but not as outstanding as he did with Manny and eventually boxed either Mercer or Holyfield at an earlier point and not been as Strong resolution a fighter as he did become, and lost again along the way because he did not lose that denial he had with Pepe.. he was a bit aloof at the time he lost to Mccall and Manny knocked that outa him, he probably would have boxed unbeaten for a lot of years but never stood out like he did eventually, Manny did make a massive difference, mostly in his psyche...
That lazy pawing jab with the predicable right hand behind and his inferior infighting abilities would have been his undoing. His true achilles heel , the chin would have betrayed him several times more. Stewart had a significant impact on him, stylisticly and mentally, no doubt.
Hard to say, but I think he'd have concentrated more on using the jab and boxing. Steward had him planting his feet to generate more power and I think Lewis went from being a guy who would take a KO if the opportunity presented itself, to one who would look for one. How that translates to his success is anyone's guess, but Steward got the best out of Lewis so I'd imagine he would have been a little less formidable than he became.
He wouldn't have stayed with Pepe Correa long...if it wasn't McCall, someone else soon would've beaten Lewis and Correa would've gone. Remember that by the time of the McCall fight virtually everyone in camp except Lewis was against Correa, and even Lewis was starting to 'see the light' there. It would've only taken one loss to end that partnership. So if Steward is out of the picture entirely, it depends who he has instead. We can't assume no-one else would be able to develop Lewis, even if not quite in the same way and level as Manny did. The wrong coach, of course, could also lead to him regressing as Correa arguably did. It's notable that Lewis's jab for instance is a lot stiffer in the Chanet, Mason, Weaver fights under Davenport than the pawing setting-up-for-my-right-hand jab from Correa's fights. So, it would depend who he got. I do think the odds would be in favour of him not achieving what he actually did though. I remember when he turned up to the Butler fight at 248lbs, 10 pounds heavier than against McCall and almost a good 20 pounds heavier than most people felt he should be at that point, there was some muttering that he was just another heavyweight without any discipline going to fat...
He would still be a very good fighter, but not as great,probably have a couple of more knockout losses as well.