Thinking about the following system for on-chain 3D NFTs. First, imagine a JSON (or XML) schema which is used to describe the materials, mesh, positions and other properties, like SVG. This is the data that is placed in the tokenURI.

Second, a viewer component package that would need to be adopted by wallets. This would intake the tokenURI data and map it to ThreeJS.

Another question is how to deal with large meshes, which would almost certainly be over the 24kb limit. One idea is to fragment them and deploy as separate contracts via a dev tool–we only need to retrieve this data during mint, after that it is etched into the tokenURI.

The ecosystem for this little file format would consist of the schema, viewer(s) and solidity libraries. I don't see a way of monetizing this without harming adoption, so work may have to be funded. Eventually, upgrades and other continuous work could fundraise via NFTs which use the format's own technology.

Would be a bet on the importance of on-chain data storage.

The schema is hard to get right and crucial for success. It needs to offer enough flexibility to enable creators to make whatever they can imagine. The more flexibility added to the schema, the more complexity ends up in the viewer.