Is it possible to hardwire the car's remote wire (the one running from the steering wheel remote to the stock headunit) to the tuner module and use the Buttons Codes display function to read DIRECTLY from the steering wheel button pushes?

Very very interesting idea.

If your steering wheel buttons are nothing but a set of resistor values (like the Sony stalk), then that might actually work. Might require some additional support from Mark in his kernel, but I would imagine it's possible.

But if your steering wheel is something other than a set of resistor values (for instance if it's a modulated electronic signal of some kind), then not only will it fail, but depending on the voltage carried by the wires you run the risk of damaging the tuner module I think.

Should be fairly easy to test. If you know where the wires are, attach a digital ohm meter to them and look.