The father/son angle is definitely there, but with the "I'm a mirror for you" stuff I think them being the same age would be cool too.
There's a couple moments the movie I think would work better. For instance when Shinzon is revealed the characters are shocked, but the audience isn't really because he doesn't look like Patrick Stewart.
Actors do better when they have other actors to respond to, when they can have a real dialogue rather than just talking to an tennis ball on a stick where a special effect will be stuck in later.
I used to agree with this until I saw Sam Rockwell's recent performance in Moon. I don't know if it's just that the splitscreen technology has improved since then. Also half of Star Trek seems to be actors having dialogues with viewscreens that aren't there, I think they would be more prepared for it than any other actors.
It worked out pretty well in Time Squared, although unfortunately with those two Picards the conversation was pretty one-sided.