Impressive as the Tua and Byrd wins were for Ibeabuchi, I just don't see him beating Lewis, so long as Lewis is properly focused for the fight.
I think Ibeaubuchi could beat unfocused Lewis, but I don't think Lewis would underestimate him as he did with Hasim Rahman. I mean, Ibeabuchi beat prime Byrd and prime, in-shape Davd Tua, while Rahman was knocked out COLD by a single punch of Oleg Maskaev. No way Lewis would underestimate Ibeabuchi, and focused Lennox was one of the best heavyweights ever, he wasn't easy to hit except of great jabs probably, but Ike's jab wasn'r as good as Mercer's one.
Lennox himself disagrees with you. He thinks he would outpoint him. From RingTV" On Ike Ibeabuchi: “I thought he would have been a good ‘opponent’ for me in terms of being tough and durable. But in terms of it being a great fight or him being a good pugilist – no. I would have outclassed him and beaten him on points.” Source - https://www.ringtv.com/596217-lennox-lewis-greatest-hits-going-the-distance/
While not impossible, it's unlikely that Ibeabuchi would have duplicated his success against the top guys. Against a focused Lennox, one who (as already mentioned) recognizes the danger, the smart money says Ike falls short. The jab. The uppercut. The spoiling tactics. Lewis would diffuse him.
Lewis was starting to slow down in the 00's. If Ike got the fight anytime after that I think he could have won based on how Lewis looked in the Holyfield rematch which was 1999. He was holding a lot in that fight and against Mike Tyson's ghost. Ike's engine , chin and pressure would take Lewis to the brink.
I don't think Lennox started to slow down until Tyson fight where he looked slightly slower than before. Before that he looked as good as ever in his fights against Grant, Botha, Tua and Rahman rematch. In the first Rahman fight he just was unfocused. As for him holding Holyfield a lot in their fight - well, Holyfield made adjustments after the first fight and fought smarter and more effective fight in the rematch. Lewis held him a lot to make his infighting less effective and to make him tire. And it was a right tactics considering that Lennox won 4 of the last 5 rounds - Holyfield has tired. It wasn't that Lennox could do nothing so he had to hold Holyfield., no. It was a part of his tactics.
If you put a gun to my head, I would say no. Just like the other contenders who were meant to be the coming man against Lewis, Ike would have gone away empty handed.
Only if Lewis came in under trained, over confident and sloppy. Then Ike s maybe in with a Mccall type shock. Other wise, Lennox gets a point win.
Ike would have had a good shot of beating Lewis. Hed be there for all 12 and it would take just a single slip up by Lewis to get in trouble. I dont think its definate that Ike would win though.
Ike was at the precipice of stepping up to championship level,, he never had the chance and we'll never know if he could.
It would be a fight I would love to have seen. i believe Ike was the only guy around then that would have had a chance of beating a focused Lennox. Whether Ike won or not he would have been the man to take over the reigns when Lennox retired.