I feel like it's a no-brainer that VRChat at some point wants to let people sell their avatars through the creator economy and get some more revenue going, which the recent 30% staff layoff clearly shows is a concern.
If VRChat wants to compete with the existing ecosystem of buying and selling avatars through gumroad, booth, patreon, etc.. then they have to offer equal or better services as those websites; allowing the buyer to download the source files to the avatar.
As a creator myself, I would not want to sell my models if my buyers could not gain access to files to make their own edits. It's an extremely common practice, especially in the furry community, to modify bought avatars into unique characters through adding their own clothing, accessories, modifying textures or manually resculpting the body in blender.
Being able to locally load an avatar before buying it would be great feature, to make sure it's functional and has a good feel before committing to a purchase.