Morbi
Scavenger
Perhaps you haven't played Smash recently, maybe you have forgotten about Falcondorf or Falco? Sakurai doesn't necessarily just de-clone characters, the fan-base of said character tends to grow accustomed to that particular play-style. If you alter it too drastically, you desecrate what players enjoyed about the character and alienate them. Project M Roy isn't even really de-cloned to the same extent that Toon Link is, as they want to retain that particular play-style. So if Sakurai wanted a newcomer with a new move-set, his first choice wouldn't be Roy. Roy would be a low priority clone, just like last time, and the time before that.You're again ignoring the fact that he chose Roy specifically to have a visually unique clone.
All of those characters could get in with a unique moveset, yes, Chrom could get in with a unique moveset, but you seem to think Roy can't get a new moveset.
He would have no reason to be a clone this time if brought back, he'd be just as unique as Chrom/Lucina could possibly be without looking like Marth to boot.
If we are just looking for a character aesthetically different, again, I believe Robin would be the more ideal choice.