As you can see, I enjoy Toon Link. But here's what I believe. I think that if you make "clones" different from one another, you can almost get away with it. Great examples are Wolf and Toon Link, who just feel different when playing as them. I don't think Dixie would be a clone, but she would be based off the Diddy model for this game, which would make her easy to program. However, I expect her to have a unique, or rather an almost unique moveset based on hair, bubble gum, etc. etc.
You're right, and I'm not disputing who is and who is not a deserving character, but when a clone is added, does anybody but people already a part of their fanbase care to play as them?
Example. I love Falco, I honestly don't care that he's a Fox clone, I'll defend him to the death. But I was also already a fan. When Brawl came out, I expected to play my mains and newcomers that I was interested in (PT, Lucario, Sonic). I had never, (and still have never) played a FE game, but I picked up Ike and loved playing as him. I never really cared for Marth or Roy in Melee, but Ike was so fun to play as, he became my new favorite. On the same point, I tried Lucas, but because of his similarities to Ness, I never really cared to play him any more than I had to. Same goes with Doc, Pichu and Ganondorf in Melee.
My point is just that does a character merit inclusion more because they are new and exciting (even if sharing a few moves), or as long as we have all the A - Listers, that's all that matters? Even if some of them aren't fun or original in the least? I absolutely don't look to be RIGHT, or the smartest guy in the room on this, I'm seriously curious whether or not people want a FUN game, or what feels like a complete game?
If Dixie deserves inclusion, whether or not she's an outright Diddy clone, then both RIDLEY and TOAD deserve inclusion regardless if they're too big/small or similar to anyone else.