Ooh 3D printing buttons is a great idea
The blanks are for parking sensors (does yours not have them at all??), rear blind, and rear headrests.
Any air ride specialist should be able to build a setup for a D2 in no time.
The thought does occur that since I'm transplanting my Allroad 2.7 biturbo engine in to my other S8, along with its ESP system, its air ride system probably wouldn't know the difference if that came along for the ride. Hmm....
This is an A6 FWD rear bag:
It'd just need adapters making to fit the D2 body and lower arm, but I reckon its about as close to fitting as any OE part. Bad news is they're about £350 each!