Good idea. The MOST makes things very difficult. I recently installed an iSimple bluetooth adapter that sounds similar to what you put in (link below). The iSimple uses an app on my iphone to set the frequency, so I don't need the display that you put on the right of the instrument cluster. I have one small button to initiate contact with the unit, and i located it on the center console just to the bottom left of the radio (easy to tap when my hand is on shifter).
I might try to add a USB input similar to what you did. Right now I have a cigarette adapter, but it sticks out of the cigarette lighter pretty far.
http://www.amazon.com/iSimple-Hands-Free-Calling-Streaming-Smartphones/dp/B00FRU5UNA/ref=sr_1_3?ie=UTF8&qid=1442655069&sr=8-3&keywords=isimple