Sean Bean was a good Boromir, but is wiry enough for Aragorn. Mortgenson is an obsessive artist type. You should read how he got into the part. My favorite of all for perfect casting- Karl Urban as Eomer. Took a bit to get into him playing Bones on Star Trek (movie), but he did ok with the voice.
Yes, I think Eomer was extremely good. I still think Sean Bean would have been okay as Aragorn. He’s a very experienced actor who’s been successful in a variety of roles. Whether he (or anyone) would have been better than Mortenson, nobody can say, since it wasn’t done that way.
He killed it playing Dredd, too.
Yes, Karl woulda been fine as well. He plays in many movies and acts well.