You'd be better buying an a8 without it as I believe it's an option depending on year abd engine. I don't think disabiling it would work as I think the door mechanism are slightly different from soft close verse non soft close.
"According to my 2012 A8 brochure, I know your car is a 2014. Soft close doors were an option on the 3.0t A8s, but standard on the 4.2 & W12 A8s.
The soft close doors are part of the Convenience Package.
Convenience Package:
Audi advanced key—keyless start, stop and entry; parking system with front and rear sensors; power soft-closing doors; and power trunk open/close"