The electronic throttle affects not just engine speed control, but also mixture, accel/decel rates, traction control, the ever important temp display, etc.
Theoretically possible. You would lose TCS because it uses the electic throttle body to operate. As far as the rest of the system goes, you would probably get a TPS fault because the sensor doesn't agree with where the ECU says the TB position should be in certain RPM range with the OEM flash...you'd also get faults in T-mode with either flash.
Generally not a very good idea. Things are getting too integrated and interdependent these days.