I personally don't think so. I think it's a very short list of fighters you can name throughout history who would be considered really good - let along great - that weighed over 250 pounds. Besides most guys over 250 would just be sloppy and out of shape. The list of guys in shape over 250 that would even be considered C or at best B fighters would be pretty short too.
Pointless. Wlad constantly comes in below the 250 weight limit. And the best fighters in the division comes in below 250 lbs. Only slobs and lazy fighters would fight above 250 lbs.
In history I think Lennox Lewis is the only non-active bonafied champion to come in at 250 or higher, and he only did that 4 times in his entire career. We can add Primo Carnera if you want, but his title reign was created by the mob.
No. IF another division was to be added, it should be between LHW and Cruiser, but that said there's already enough divisions as it is.
No - just impose some sort of physical standard expected of professional HWs. For example, if you come in at 80% body fat, I don't think you should be allowed to fight.