Recasting Frodo and Merry: couldn't agree more.
THe names that pop up for me are
Mel Gibson (as Frodo) and
Kenneth Branagh (as Merry.) Or you could flip the two.
Why choose them: maturity, depth, gravitas. Humor beyond mere silliness. They've both tackled Hamlet (haven't you ever imagined Frodo pacing, ring in hand, debating
to be or not to be...?) I also really enjoyed Branagh's Henry V.