wow, just found this thread again and had lots to read!
I think it is a very safe bet to say that you have the most involved car install that we have so far. Or will have. Definately take pictures!
What is it that your software is trying to do?
And the debugger came later.
I think the first thing I did if I can remember (I cant believe it has been almost a year since I started working on this software ) was create the global lists, to support the outputs and inputs. Then got the GUI to control what should happen, and then translated the should happen to is happening through the USB code.
Debugger was added after it was communicating with me using breakpoints and manually entering a byte stream to send off, or manually reading the binary stream being returned to verify what was happening. Then I made it easier to manipulate through the debugger.
Speaking of software, I need to get back to work!