That's our prince! Thanks dude!
Concerning Lucina, I think an alternate costume for Marth would be cool, but it's something Nintendo might not do. This is simply because it you compare Marth to Lucina, their colors are essentially identical and in order to accomodate for Lucina's hair (of all things, yes it's the hair) or (debatably, because Marth is so skinny) her body shape, they'd have to draw up a new wire frame and some additional animations, which is a lot of extra work for a project this big (smash as a whole, and now two versions). Now that I think about it, even Marth's awakening costume, being so radically different might require a different wire frame, so that might not even be an alt.
Ultimately as much as I want to see the Marth variations as alternative costumes, it's just not practical production wise for the team to give this kind of attention to EVERY character in smash. Wario is the only one who actually had an alternative costume in the last game besides a simple re-color (if I'm mistaken, please point it out, no Dark Link is a re-color). This is probably because they already had a Wario model on hand from somewhere else and it was easy to slip into production.
Marth's case simply isn't like that, since the only 3D models of Marth that exist are the models in Smash and the fighting animations from the DS games.
EDIT: I have a feeling Marth's voice will remain japanese. This is just a hunch, because most Smash Veterans' voices remained the same from Smash to Melee to Brawl. There is no evidence to support this however. They changed Fox, Wolf and Falco's voice to English, then again they also speak a lot more (with voices) within their games. Fire Emblem (Marth's games anyway) is not known for this (If awakening voices Marth, tell me. I haven't a 3DS)