Well, I think what you're thinking of is VERY doable. You just need to splice into the HU audio conection wires and you're golden (you need to install a switch though because the HU has different voltage output than the Riocar).

The only thing that I think would be kinda tough is making a custom plastic bezel to fit around the opening. Otherwise it'll just be sitting there lookin' kinda ugly.

Here's a tip though: You'll need the HU to stay ON while you use your Riocar otherwise the amps will shut off... Unless you buy yourself an Audiolink PD4 and split the BOSE connectors completely into a Y configuration.

Hmm... Now you've got me thinking that maybe *I* should do this.