You can get somthing called a video in motion adaptor.
As far as I know, the radio stops playing video when it detects the speed over the can-bus network.
On the back of the radio there are 2 wires marked canH and canL.
It might be worth seeing if you can pull the wires out of the multi-plug (but do it so you can get them back in again) and see what happens.
If it can't get a speed signel it can't turn off!
Only problem is, you will lose gala,wheel controls,on/off switching and the dash display.
But if it works it might be possible just to put a dp switch on the can line so you can disconect it just when you want to watch a video?