Well, the most obvious change would be that instead of Shinzon's ridiculously convoluted plan to hide B4's parts all over a planet filled with dangerous natives that could most likely kill Picard while he's on his silly jeep ride, they could just have had Shinzon raid whatever place Lore was kept, steal Lore, reactivate Lore, and then try to replace Data with Lore while the Enterprise crew was in orbit of Romulus.
That doesn't really work for me. If the Enterprise crew knows that Lore has been abducted then you'd think, given their previous encounters with him, the very first thing they'd do is ensure that security protocols were in place precisely to prevent Lore from imitating Data again...especially as they already fell for it at least once.
I suppose you could further finagle things so that the E crew
doesn't know that Lore's been taken, but it feels like the credibility level of this story keeps dropping.