It would be a close fight, but something is telling me Weaver would pull this out late, by 13th or 14th round stoppage. Though Ellis has an almost equal chance of decisioning Mike.
I would go with Ellis on a 15 round decision. However, a fact one has to look at is the fact that Weaver is a very slow starter and Ellis is a very fast one. Indeed, Ellis' record is littered with early KO's. Just something to think about and not something that would go unnoticed with their respective trainers and corners.
Mike Hercules Weaver was given a boxing lesson by Big John Tate on the night of March 31 1980, then in the 15th round, Big John came crashing down on his face, the referee could have counted to twenty instead of the usual ten seconds. Mike was the new WBA World Heavyweight Champion of the world. Jimmy Ellis was also a WBA World Heavyweight Champion, he was crowned on April 27 1968, after defeating Jerry Quarry by a majority decision, this after stopping Leotis Martin, TkO 9, and defeating Oscar Bonavena, by unanimous 15 round decision, even after scoring a knockdown on Oscar. This was The WBA Tournament to find a new champion following Muhammad Ali's conviction of Draft Evasion in 1967. Weaver is a slow starter, but can hit, as seen against WBC World Heavyweight Champion Larry Holmes in 1979. Ellis with a snappy left jab would keep Mike at a distance by circling as well, throwing quick combos as directed by his trainer, Angelo Dundee. Jimmy aware of what happened to Tate, stays away to score a unanimous decision win.
I politely disagree, Dundee had a prime James Tillis challenge Weaver for the WBA belt. Once Tillis felt Hercules's power he ran like a rabbit all night and lost the decision, with Angelo going crazy between rounds and screaming profanity at Tillis.