How about Uma Thurman as "the" villain of the movie.... that would work well with her "Kill Bill" persona.
Discos had a good point about the "timing signatures" of Tarantino versus the traditional Bond movies - I think that the linear chronology should remain in tact. After all, with QT directing - that in itself will be an adjustment for many fans (not saying it's good or bad - just an adjustment).
As for special FX - don't mind them either - they just shouldn't be the "whole" movie. How many people truly remember the Bond movies for the "compelling" or "memorable" stories!?
It's like "remember when that bomb went off in the....." or "remember when they narrowly escaped something-er-other"