What exactly was the point of the scene where they find B4 and are chased? What would have happened to them had they been caught or killed? What was Shinzon's plan with that?
Shinzon's plan was to wait until he was a week from death, then lure Picard with the lure of exciting offroad action so he could capture Picard. Shinzon likes playing the odds, you see.
It's unclear what would have happened if 1) the Enterprise failed to notice the positron emission, 2) the Enterprise did the prudent thing and took several weeks to return B-4 to a Starfleet research facility, 3) Starfleet sent regular ambassadors to meet Shinzon instead of Picard, or 4) Picard was killed while playing dune buggy.
I doubt there was a backup plan for any of these things. I suspect the Shinzon would have hit the fan.
This is just a tiny percentage of my fridge logic moment about an hour after watching NEM at the cinema. Most of it started with "wait, why the hell...."
I believe most points are valid, but what bugs me the most (if I bother to think about it) is the lack of coherent motivation for anyone in that film.
Nevertheless, I still watch it from time to time, and am able to get some level of entertainment out of it (mostly I watch it when I visit my parents, who love it to bits. It's become something of a tradition)...but the film is not a very good one at all, to put it mildly.