Tiny characters.

I imagine if they were to respect the original scale, the small sidekick would be a disc you place under your hero.

So for instance, say you have Woody with Rufus, he'd pull Rufus out of his pocket when you need him.
If that was the mechanism they employed, you wouldn't necessarily need his partner, just a main character to carry him around.

Going to problematic for the Incredibles though, their uniforms don't have pockets!
Maybe they should ask Edna Mode for utility belts.

I doubt if Princess and the Frog gets characters, we'll see Frog Tiana and Frog Naveen.
After all, that was the result of a

Spoiler: show

curse

placed on Naveen by Facilier and well, even if they overlook the fact that he is

Spoiler: show

dead

, I doubt Naveen would be foolish enough to get turned into a frog again. Especially since it would be real easy to break since all it would need is a kiss from Tiana to change him back.
See the movie ending for the explanation of how.

^ While reading through this topic I was thinking exactly what you wrote.

they could be about the same size as the cars because remember they are toys and if you got a figure of Sebastian it wouldnt be that small would it?

Well, Toy story characters should be small but they are a fine size, probably the same as if they made your suggested figures.

What I'm hoping is the in-game counterpart of the figure works well.

So let's say you did have Sebastian, he should be tiny compared to Sulley, and to do that they could just have the camera zoom into him so he looks average size for the player, but when standing next to Sulley he looks tiny.

If they were to make him as big as dash.. it just wouldnt look correct. Toy standard with the figurines would be okay, but the ingame character would have to be smaller IMO.