Well, I fleshed out those two rules I mentioned a few posts ago. The first one pulls upon the ballot's one and only verified rule, and the second just pulls from business logic..:
1. The character has to have originated from a video game
That rule is arguably one of the most notable, and important. In fact, it was the only rule specified for the ballot. This rule basically feels like a safety net put up by Nintendo. They knew they would probably get a thousand troll characters, and get suggestions for non-video game characters, so they probably set this up.. lol.
So basically this rule means:
A. Characters who originated in anime/manga media aren't eligible. (Naruto, Goku, Ash Ketchum, Inuyasha, etc.)
B. Characters who originated in movies/animated movies aren't eligible. (Shrek, Wreck It Ralph, etc.)
C. Characters who originated in cartoons aren't eligible. (Spongebob, Mickey Mouse, etc.)
D. Any other characters who originated outside of gaming in general aren't eligible. (Storybook/book characters, Real people, etc.)
2. The character has to sell
Obviously, this wasn't "mentioned" as a rule, but it's definitely something that would be a key factor, no matter what.. as it would ultimately decide whether the character was worth the time or not. This, is arguably probably one of the main reasons the ballot was started to begin with..: So Nintendo could get an idea of what characters, were heavily popular, and which ones didn't receive votes at all. Sorta like a "which characters have profit potential" sort of thing.
So basically a few things flesh out from this rule:
A. The character must have a notablely large fanbase. (Again, this is based off of the "is the character profitable?" question. If a character has a large/decent fanbase, they would probably be more interested in the idea... luckily, the nature of the ballot in general helps with this aspect anyway, as the ones at the top will probably receive the most attention.)
B. The character must work as a fighter. (Of course, even though this is fan service, the character still has to flesh out as a fighter. The reason for this, is simply this: No matter how much a character is requested in the ballot, if they don't play well, or work horribly as a fighter, that could affect their profit potential. Some "might" buy them just to have the character, though others might see that "this character sucks" aspect as a turn off.)
So did Sora, but it's obvious why he'd never make it in.
Again, we still can't make any assumptions. I still personally don't see legal issues as much of a problem at this point.. as I'm fairly sure 100% of all 3rd parties and indies LOVE the idea of profits being generated from long term paid DLC, from a very popular Nintendo game.. not to mention the publicity the character would get.
The only way I would see Disney turning down the opportunity, is if they had Sora planned for some Disney Infinity related scheme.