Literally the only problem I have with Toy Story being a world is if they decide to give SDG a "toy" makeover. Sora would look fine, but mother of God can you imagine what Donald and Goofy would look like as shiny plastic figures? Don't know about you guys, but it looks creepy in my mind.
If you have any toys of Donald or Goofy I think they look just fine Nobody said that the toys would have to be made of really shiny and squeaky plastic. Vinyls exist and even if not those, a lot of figure don't shine
Toy Story is the only Pixar movie I can imagine doing well as a stand alone world. Cars would be too awkward, maybe a mini game world or references in the "parade". I know a lot of people like Up, but I can't help but feel it wouldn't work in KH, not a main entry anyway where they need to focus on the best and most varied Disney worlds. That's also why I'd say no to Nemo and Monsters Inc. The worlds are awesome but they are too similar to what's gone before (Atlantica and then dressing up as monsters in Halloween town.) I wouldn't be against these worlds, I just think the places are better reserved for more classic Disney and some of Disney's less known films like Return to Oz.
You forgot a few movies there like the Incredibles (which I know does counter a little bit with the family theme but they do work) and more importantly Brave (since I think Brave fits VERY well). Merida could easily serve as another feminine hero as we need more of those in KH and the world Brave took place in is pretty new to what we've seen before. The old Scottish (or even European) castles and towns are something we haven't seen in KH yet and I'd love to hear Shimomoura take a spin at Scottish music.