I was considering that the data characters don’t actually have bodies underneath their clothes at first. So like RI couldn’t unzip his coat, and Sora couldn’t take off his jacket. There would just be voids underneath. So when coding outfit skins, it really is full a neck-to-toes render that has to account for both where literal clothes are, and where the “clothes” are seen as flesh. But hunting around for existing skins that have all the bits of exposed body they want in order to build new skins is a pain. So they decide that first things first, they need to figure out how to modify their base programming so they have a full body shape, which they can then use as a base for building skins (including “painting-on” flesh where they want it). The bodies are completely black at first, because it’s the simplest render.
They end up really liking the freedom of movement, both literally and from a data point of view. The less complex the character render, the faster and more smoothly it can load and move about. They eventually add the colored trim and other details, mostly just cuz they look sweet and don’t take much more power to render. So the catsuits become their default outfits, because they are the most efficient skin. Even appearing buck-ass nude would take more power, because of all the textures you need to simulate skin and body hair and stuff.
They briefly look into making clothes simply objects they can interact with, starting with RI’s coat. Which is why you can sometimes see him running around in his finished catsuit but with the coat over top, unzipped different amounts. But man, why go through the hassle of physically putting on and taking off clothes, when you can just slap your chest and apply a skin? Besides, full skins come with that benefit of being able to hold abilities. So ultimately the catsuits are their base, default forms, and everything else is a skin applied on top. Except Riku’s coat—that’s just an object now. Which, full disclosure, he only put back on because he was worried about what User Sora would think of him when they first meet during the escort mission. I mean he’s not only a weird little clone of Sora’s best friend, he’s been modified with eyes that some Users report as being “creepy.” So he keeps the coat zipped and hood up until ANSEM’s teasing and Sora’s… Sora-ness convince him to open it. But since it’s an object, he still has to haul it around until they get back to the Datascape proper.
Also since I am addicted to fabulous costume changes, I figure that once they really get the hang of making skins, they start making different outfits for different worlds so they blend in better. Sometimes you just wanna visit a world as a civilian to hang out, y’know? (But everyone else is programmed to not notice the facial oddities ;P) It’s just always annoyed me a bit that very few Disney characters in KH ever mention how absolutely ridiculous and out-of-place the KH characters look. Like I know that conversation would get real old real quick, but still. “Ah yes, a child in red parachute pants and giant, monstrous animals. Seems legit.” May as well at least put on some more "normal"-looking clothes depending on where you're going, right?
As a final note — just a point of interest, really — this whole “skins” thing occurred to me because of data!Riku’s reveal in the game. It seemed pretty overdramatic to do the whole fancy-pants digital removal of his hood, instead of just reaching up and pulling it off. But then I was like… maybe he literally can’t just pull it off. Maybe “hood-up Riku” and “hood-down Riku” are two different models, and he had to swap between them. Not saying that’s actually true for canon, just that it’s a mechanic I’m using for this AU that’s “supported” by some canon events.
