Asteroid rings are included in the sense of rings around gas giants, sorry if that caused confusion with asteroid belts.
Asteroid belts are a great idea though, they can be implemented with a VFX graph system with a few unique meshes for the asteroids, spawning them procedurally with randomized scales, sizes and rotations. I actually have individual mesh based asteroid generation in a private system, so I will definitely prioritize cleaning it up and publishing it as a system for Procedural Planet Generation.
