A lot like some people in other threads, your point is based on the possibility of editing an already established labelling and info.
If you know Sakurai, you would be aware that he is extremely consistent and pays attention to detail. Even in Smash 4 you never had him go back and change something like this. I really don't think this is the case. It's VII or go home for him.
Uhhhh... They only took AC as a skin and Cloud's visual appearance from Dissidia. Only his dash animation is from that game. The rest is more faithful to his game incarnation than most other appearances. Sakurai is, thank goodness, looking at the original game (the only one that matters, specially considering the expanded universe is not only garbage but isn't even canon to the remake), so if he made Sephiroth, he sword would be long, but not pathetically huge like in the expanded universe joke.
Actually, you're wrong. All of the summons use their FFVII design.