A young George Foreman was a lot of fun to watch, but lets look at the facts.
A prime Foreman relied on his physical size and strength in an era of smaller men. At his peak he was a hair over 6'3 and between 215 and 220 pounds.
David Haye lists at 6'3 and weights in about 5-10 pounds less than the young Foreman.
Let's not also forget that Foreman was completely outboxed and defeated by what would have been a modern day Cruiserweight in Jimmy Young. I rank Wlad quite a bit higher than Young.
Foreman has always been critical of guys who are anything other than face first brawlers with no regard for defense. That is what he was, and that's what he had an easy time beating. The guys who boxed him took him to school and he didn't like it then and he doesn't like it now.
Klitschko would most likely jab Foreman and keep him at bay and let him tire himself out in a less artistic way than Ali did it. Foreman couldn't be ruled out, but it's actually one of the hypothetical historical fights that I think would suit Wladimir best.
As far as fights that would be awesome to see. How about Vitali vs a young Foreman?