So I looked into this. Allowing users to upload with #IPFS, a decentralized protocol replacement for #HTTP. Currently, I am benchmarking it by replacing my #Redis servers with it, just because I can for a few weeks.
#ActivityPub can be extended to allow for some extra allocated fields, and a fork of #Mastodon can be made.
Users will be able to upload their designs, and hosting would be decentealized and automatically spread around all users.
It is possible. I will look into a prototype, allowing users to use a bot or something like @3dprinting to share their prints before going for a fork of #Mastodon. Also need to investigate existing Activity Pub solutions and would possibly use something like #Go for the backend.
I'm still deciding on the front end.