Oooo I wanna join in too! I can't find your original post
Evil Trapezium
but here goes:
Capcom: Dante (Devil May Cry). This character is very unique and because we already have Mega Man and Street Fighter representation, I feel the Devil May Cry series is next up for Capcom representation (aside from Monster Hunter.)
Namco: Lloyd Irving (Tales of Symphonia). I feel as though this character is long overdue to make an appearance in Smash. Lloyd would have a unique, fresh moveset, and I think the fact that his Mii Costume hasn't returned yet is a pretty good sign.
Nintendo: Dixie Kong (Donkey Kong Country 2). I would agree with you if you were to tell me that the Donkey Kong representation in Smash is complete, but I can't help but feel Dixie would really round it out when it comes to the main Donkey Kong characters. Having a Diddy-like character with different physics and unique moves from the DKC series would be awesome! Dixie has so many moves to pull from, and would be more welcome female representation.
Third Party: Crash (Crash Bandicoot). This is one of those legendary characters that would blow many minds, while also fitting the Smash aesthetic perfectly. It's not hard to picture Crash as a character; like Banjo, Crash has a moveset made for Smash. Crash is also one of the more popular 3D platformer reps, a gaming legend. I would love to see him added.
Third Party: Castle Crashers (Castle Crashers).
This game was a ton of fun, and so are these characters. If they were to somehow get into Smash, I'd imagine the character would be a gray knight with the abilities of the four main characters if that makes sense. Gray knight could use poison, fire, electricity, and ice. In addition, they could also pull from the moves of the other playable characters for more attack variety. Alternate skins would be the different knight colors (red, blue, orange, green, pink, purple, etc.) This is a major pipedream of mine, but I think they'd bring a new level of fun, uniqueness, and variety to Smash.