In response to the latest blog post, I shall throw my own ideas and opinions into the discussion. Characters whom I would like and think qualify include:
Mewtwo
Pichu
Black Shadow/Ganondorf
Leon Powalski
Ridley
Fusion Suit Samus
Sukapon
Waluigi
I agree with a lot of your ideas.
Mewtwo is a given.
Pichu I don't think anyone wants. And we have
enough Pokemon, especially with Mewtwo.
For
Ganondorf, the trident is a cool idea,
but 1) that was used by
Ganon, i.e. the pig form, only, and 2) I don't think there's been a model done for that (though I guess that's more minor). Anyways, Ganondorf doesn't
have to have swords. Maybe it could just be a few of his attacks, and not necessarily his whole moveset like Marth. I'd like to see him use more magic, which I think is the key, and what he's been sorely missing.
Leon... meh. We have enough Star Fox. He
could be possible as a quick addition much like the original 6 clones were, but you might as well use that to time to clone someone who hasn't been cloned.
Ridley is an awesome choice. There's already a lot of material on Ridley too out there to base things off of.
Fusion Suit Samus - I would be pretty unhappy with a THIRD version of Samus.
Sukapon - By far my favorite choice, and I've been wanting him since Brawl. His biggest con is that he doesn't have much fan support (although that can be due to his lack of exposure, which you can also turn into a pro, as you mentioned). I've played Joy Mech Fight, beaten it, and loved it... and the only reason I played it is due to Brawl speculation. If they can do for Sukapon/JMF what Ness did to Earthbound, that would be awesome. Now his second biggest con is programming him, since he'd have to be from scratch. However, the plus side to that is that his animations are probably as friggin simple as they get due to his character design.
If there was one character made from scratch, Sukapon would be the easiest to make (at least I think so. Plus his game already gives him a moveset, with specials!
Also, Sukapon could be the "Well you can't have an awesome blue robot made by a doctor to stop robots gone haywire by an evil doctor, BUT you can have an awesome pink robot made by a doctor to stop robots gone haywire by an evil doctor" character, if you get what I mean
Waluigi - I never thought he deserved a spot on Smash Bros. He was never significant in any important Mario game... in fact, he isn't in ANY Mario game that isn't a party game (still, wtf Nintendo). His lack of a role as a primary character, antagonist, or extremely important supporting character (like Peach, Zelda, and Metaknight) would exclude him normally. That said, he's one of the most well-developed custom characters in terms of PSA and model, so the amount of work with him shouldn't be bad as making someone from scratch.
I'll also throw in
Little Mac - However
unlike Sukapon, he'd be a pain to make from scratch since you'd have to do all of his animations.
At least he's already in as an assist trophy though, so he'd have one attack done already...
So my personal order would be:
1. Mewtwo
2. Sukapon
3. Black Shadow & Ganondorf
4. Ridley
5. ...Waluigi
6. Little Mac
I also think that Pokemon (outside Mewtwo), Fire Emblem (I'm looking at you, Lyn+Ephraim fanboys), Star Fox, and Kirby have more than enough representation and don't need anymore