This weekend I finished assembling and painting the chassis and I'm pretty happy with the results. It looks much better than the original version at least.
The motors and ultra-sonic sensors are installed and everything is looking pretty tidy so far. I made custom 3D-printed mounts for the ultra sonics so that they would sit flush with the wood and to help secure them in place.
Now I need to take a step back and figure out the plan for the rest of the electronics.