Thank you for sharing your project.
Have you had any field time with your setup? How is the reliability of the wireless link?
Have you seen the quick-tach motor holder project? It uses a dovetail and pin to mount the steering motor and makes the steer motor easy/fast to swap between tractors. It would go nicely with your setup. Universal Fit Gear System, with Quick Tach Motor Holder
Things that I really like are the fuse holders, laptop voltage converter, and the idea to mount the PCB to the tablet. These are ideas that can be used by anyone.