Man, it's been a couple years and I can barely remember parts of what I did. I left the tilt ECU in place and just fooled it by disconnecting some sensors and disconnecting the tilt lock motor.
Maybe all the lights were out at one time but a tilt light has come back on. The bike rides fine though, it's not stuck in idle.
My 'manual tilt lock' hack eventually failed so now the MP3 has no tilt lock at all. It's fine to ride it, but just a bit tricky to get off and get it on the centerstand. Not too bad.
The research project is over and the MP3 mostly just sits around. If anybody wants to make me an offer on it let me know. It's rideable as is and I've got almost all the parts to return it to stock.
How did the research project turn out, you ask? We built at least 4 prototypes of different leaning 3-wheel vehicles, from scratch. We also hacked the MP3, a Honda Gyro, and some other stuff. It was a lot of fun. You can see where we were headed, here:
https://nimbusev.com/
Sorry I can't tell you more about deleting the whole system. On a modern computer controlled bike that's probably a complicated job. If you have a carbureted bike or maybe could get an ecu off some bike that has the same engine but no tilt system, it might be do-able that way.