Was looking for the VSS on the driver's side and came across this install in Japan.
http://abbey370.sakura.ne.jp/car_custom_audio1.html
http://abbey370.sakura.ne.jp/car_custom_audio2.html
http://abbey370.sakura.ne.jp/car_custom_audio3.html
So it looks like it is practically possible to install a double din unit into one of these.
Doesn't appear to be for the faint hearted but it is possible. Maybe there is little more than disconnecting the PCBs and extending the ribbon cables - or would that be too simple?