Haven’t really read much of the thread, but I figured I’d put in votes based on what info the OP gives
Plusvotes:
+Bowser Jr.
This just sounds like the funnest thing in existence, to be honest. I love Bowser and think another spin on him would be great.
+Isaac
One of my favorite games growing up, so it’s a no-brainer vote for me. He'd be fun to play, as well.
+Lyn
Also sounds pretty fun. Not a fire emblem fan (I find them to be horrible examples of their genre), but a fan of their smash incarnations. Playing a swordy woman is pretty much one of the things I want most.
+Dark Samus
Sounds like she’d have a really fun and somewhat easy to brainstorm moveset, and look really cool to boot. Metroid needs more reps.
+Ridley
Again with the Metroid reps thing. Have you seen that Ridley in the Melee opener? I want that. (but only if it can be done to a near perfection, somehow.)
Halfvotes:
.5 Pichu
Wow, how unpopular. I like the guy a lot personally, but not enough for him to be a top priority.
.5 Dixie Kong
Again, not a top priority, I don’t even really play Diddy. I like the idea of Dixie as a character though (and of more femme fatales).
Downvotes:
-Black Shadow (F-Zero) and Ganondorf(Legend of Zelda)
Completely against this. Plastering Ganondorf’s current moveset over another character model while giving Ganon a new moveset just feels wrong. I’d probably stop playing Project M entirely if that happened; it’s definitely not something I feel like is in the spirit of this game. Part of the reason I like Ganondorf at all is because of his Melee self, he’s a relatively rare sight in games honestly. Perhaps I’m alone here, but I feel I could never get used to it, as a Ganondorf main.
-Shadow
If there’s a way to seem unprofessional, it’s this. I don’t think he’d be interesting enough or is iconic enough to get in. The only other viable sonic character I’d want less is probably Silver.
-Tails
I feel like if there’s a guy iconic enough to deserve this, it’s Tails, but I really don’t think we need to increase 3rd party representation.
-Knuckles
Would be the most interesting to play, and most fitting in a fighting game. Iconic too. But, I honestly wouldn’t like more sega characters in general.
Neutral to all else.