I went back and read jimlab's thread on the S2000 pushbutton start and noticed that he had the similar issues with what I have. It seems that there is a logic needed for the ECU to "see" the stock "S" terminal connector in place. As I said in my post on 'starter trouble' I get the airbag and brake warning lights, where jimlab got brake and ABS.
I guess this gives me some indication that the transmission inhibitor switch is not malfunctioning, and that it likely IS the ignition switch.