Cruiserweight 175-195 (there's too much of a gap b/w 175 and 200)
Heavyweight 195-225
Super Heavyweight 225-270
Titanweight 270+

I think that's fair, and more appropriate to the diversity of heavyweights out there from all over the globe.

Alot of the oft criticized overweight heavyweights would have to get fit to make the 225 limit, as they wouldn't want to be sticking around in Klitschko territory.

Presumably there would be no minimum weight requirements for super heavyweight or titanweight championship fights, so the smaller guys could take on the challenge if they are good enough.