Thanks for your ideas. It is nice to see I am not the only one searching for a devide like that.
While searching for it I found some more stupid combinations like 1-din in-dash VGATFT + TV.
It seems more logical to have current 1-din in-dash VGA TFTs available on its 2-din equivalent format

. Same way like multimedia car devices are available in both formats.
Of course a unit like that should provide some minimal extra functions like radio tuner & stero amplifier because it would eat both din holes.
But I am just wishing, I undestand it does not exist. I have not too much time to spent in modifications, so the only thing I could use is an in-dash unit...