Congrats for the big job!
Interresting to see your effort in that direction, as I'm precisely going away from my iDrive.
I don't have the Combox, so no bluetooth nor album covers...
I like the "vanilla" and OEM style, but to me the Navi is clearly outdated, and my main motivation was to get Waze on a real screen (bored of sticking my phone on the air vent).
So I juste installed last week a freshly received Android 10 Head Unit, and I'm pretty happy with it
But yeah...no flip screen anymore...
For your info, there is a 4-pin wire at the back of the screen, to control the motor I guess. Video signal is handled through the LVDS connector I think.