If they revive Blofeld, he probably needs to be tweaked a little bit. The Austin Powers trilogy pretty much took the menace out of an evil bald guy in a Nehru jacket stroking his pussy. Give him a lizard like Sanchez perhaps?
In keeping with tradition, he face shouldn't be seen right away. Max Von Sydow could do the voice, if the Bond people don't hold a grudge about him being in Never Say Never Again. ;)