Hello,
Unfortunately, I cannot provide real numbers but when I did some searching and browsing for a Hauptwerk-based instrument in January/February, I got the impression that most manufacturers providing a solution with an integrated touch screen, go for a 4:3 ratio. Consoles (and users) with external displays mostly seem to use 16:9, which - as you said yourself - are the industry standard at the moment. On these wide screen monitors, there's usually a black padding zone on the left and right side of the screen.
It seems to me that providing (next to the real world screens) a simple, very graphical interface (thus, less realistic) is a good fall-back solution for all screen sizes, esp. for very large organs.
Regards,
Michael