To Cless who said Marth was a weak Lord - True. However, it doesn't change the fact that FE1 Falchion was the absolute most BROKEN sword ever. It made Marth unstoppable in FE1 because of that. You can't judge a character in terms of stats, you need to take into consideration the weapon they use in battle as well.
In regard to this topic - Roy was a trashy character in comparison to Marth. While Roy had some favorable effects with some of his attacks, such as his Counter being favorable over Marth's, it didn't save him from being as good of a character as Marth. It's already evidenced by Ike having some flame elemental attacks, such as Super Aether and Eruption, and having a broadsword fighting style that Roy likely won't show up. Those two key traits were what WOULD have made Roy different from Marth, taking for granted that he would be de-cloned into having an original A-Set and B-Set.
IMO, Ike replaces what would be lost by throwing Roy away, and then some.