After a few months away due to a move, I've started to pick up more work on this project and have gotten my prototype operational. I still have several things to add - I'd like to move the electronics to the bottom of the printer, add a third Z motor, and get it enclosed. It's getting there, but I'm thinking I'll be several months out from the final product at least. The video below shows it printing at 150mm/s, 11000mm/s2 acceleration. I have since flipped the motion system around so that the belts aren't crossing in the front, and the motors mount in a way that they act as belt tensioners, similar to how Voron does it.
I've got a rattle somewhere in the toolhead, but I don't plan on taking it apart again until I swap the motion system out with the new design and replace the hotend with a Rapido.