Avatar, also, proves that you don't need Earth to hang in the balance, or much of Earth at all, to make a successful science fiction film. (Note: I don't like Avatar, but it was a mega huge hit, and people were damn near killing themselves over the emotional connection they had with a completely alien species and planet that had no connection to Earth at all.)
I would honestly totally rewrite Shinzon as a character. I'd cut out the whole Troi subplot, i'd cut out the dying subplot. Instead his focus would be entirely a Hitler-inspired ideology of genocide against the Romulans. The Enterprise would, much like her predecessor in Yesterday's Enterprise, make a last ditch stand. This time, defending the Romulan's from Shinzon's radiation weapon.