I haven't thought it through completely, but it could start out as basically dall-E but for 3d meshes. Then what would be really useful if it could faithfully represent some specs you give it. Dimensions, shape, etc. Imagine all the specific instructions someone who knows a lot about gears (but nothing about how to use CAD) could give as a prompt. All these specs should be followed faithfully. It should be able to create any arbitrary gear you describe to it. Gears are just one simple example but you get the idea.