Haven't heard of it or experienced that mate. Does sound like a loose cable though, or the unit has some fault and a decent jolt makes it crash and restart.
I have put some serious thought into pulling out and changing the standard stereo with an aftermarket gps unit though. I quizzed my dealer pretty hard on it when I bought the car because I was considering having them do it. They suggested a few brands that have worked for them and confirmed you can definitely keep all the functionality of the steering wheel buttons. There was a JVC, Kenwood, Pioneer & Alpine model they mentioned so it pretty much sounds like anything that is designed for steering wheel controls can work.
Aerpro make a replacement fascia for the MQ to suit a standard Double Din Stereo and the wiring adaptor specific to the car that you would need. There was another thread on here to do with the stereo removal
viewtopic.php?f=101&t=18539 and it looks like the guy was successful but not a lot of details.
take some photos if you start dismantling things to help the rest of us:)
There are two types of people in this world; those who can extrapolate from incomplete data.