Update:
As of UE 5.6 Prevew Epic has added “Fast Geometry Streaming” which is an implementation described in the CD Projekt Red presentation video linked in my original post. You could use a system like this but figure out a way to feed your procedurally generated proxies at runtime instead of it loading them from disc. I’m sure they’ve provided interfaces or overrides to do things like just like this.
Original:
This might dive deeper than you intended, but have you watched CD Projekt Red’s talk on working with Epic to extend Unreal Engine for streaming static world elements?
They tackle Streaming Stutter by bypassing Actors and Components for most open-world geometry. Instead, they use lightweight POCO structs (called TurboEntities) that solely manage corresponding RenderProxy and PhysicsProxy structs. These run on worker threads via their Entity Jobs system, allowing 95% of the environment to stream off the main game thread.
For procedural generation, you could adapt this by generating TurboEntities on demand instead of streaming them from disk.