You can use Alembic layering to write out a cache of high-res RBD pieces once, and a separate cache with the low-res proxy transforms whenever you update your sim/post-sim tweaks. When reading it back in, load the high-res pieces, and layer the low-res transform data on top.

With packed geo, alembic will use the pieces' transforms instead of deforming the geometry each frame. This makes the cache a lot lighter and quicker to load.


** I had to lock the Alembic SOPs to upload them here. You wouldn't want to do that in your own setup, or you'll lose the animation.