Samus has had the same moveset in every game, this would make Dark Samus a direct clone, and even most of the new clones in Brawl were just semi-clones. Sure, her moves have worked a bit differently in every game, and in Melee she didn't have ZSS, but this would still make for the most uncreative clone since Melee even with added phazon effects. If DS was implemented as a clone, it wouldn't be too much to expect her having at least one or two moves that work differently from the original character, like almost all clone characters have at this point. And if you're just going to give her a moveset from a character whose moveset has never made any drastic changes, what's the point in going back and just copying it from another game, when development could just differentiate her from the current Samus?Ever hear of "retro" versions of characters...?
Just give Dark Samus one of Samus' old movesets (i.e. her Melee one), add Phazon effects, and there you go.
Sorry if I'm missing something, but this doesn't seem to be a new idea, it just seems to be something that was done alot in Melee, and is unlikely to happen in SSB4.