I think I've pretty much finished updating the thumb clusters. I added an .stl and .f3d assembly export for both thumbs, along with an online viewer thingy (links: left, right). And the kicad designs for the PCBs have been updated.
I'm currently waiting on a digikey order for the optical components, to be able to verify the optical performance of the finger and thumb clusters. That order also has some Saola ESP32-S2 boards that I want to play around with, and see if it might be feasible to port the QMK firmware to.
I'm holding off on starting work on the central PCB for now, since that will depend a fair bit on what dev board I end up going with to drive it.