Nemesis isn't as bad as it's made out to be imo. It was the first Trek film I saw in the cinema (I was 11 I think). Looking back now, I find Shinzon boring. But I liked the idea of the Remans, I love Romulans (real ridged Romulans mind you) though they deserve much better representation in a movie. And of course, it had Admiral Janeway. I wouldn't change too much about it, though I'd make the antagonist Sela, maybe have a fleet battle, throw in one of those D'deridex beauties.