Firstly, there should be a more descriptive error message that pops up if an upload fails due to the authenticated user not having the permissions to override an ID.
Also to waste less of their time I feel like the SDK should check if a user has permission to override the ID at least before giving them the whole upload page to write and place the camera.
I've noticed that a lot of avatars that people buy still have the avatar ID from the creator's own upload when they packed the unitypackage. This would help save time and avoid confusion.
I'm mostly thinking on the avatar side of this, but while less of an issue, I'm guessing it can also be one on the world side of the SDK.