OK, Since I've accomplished retrofitting OEM A8 D2 MFSW and several folks have asked about it during annual meet:
1. You can control RNS-D and RNS-E with steering wheel buttons. Previous, Next track/station, volume up/down
2. You can control RNS-E bluetooth telephone unit with steering wheel buttons, i.e. browse phone book which is displayed on DIS (both names and phone numbers), initiate and end the call
3. You can initiate voice commands for RNS-E (push-to-talk button).
4. Steering wheel heating feature can be connected to driver seat heating switch.
5. There are tiptronic buttons on the wheel too.
Very detailed instruction how to accomplish this retrofit is here in PDF format:
http://www.motor-talk.de/forum/aktio...hmentId=695282
Document is about A6, but everything matched my car, including all part numbers, and I've checked all my steps with ETKA and ELSA wiring diagrams.
(tried to upload PDF file directly to this post, but it is 1.2 MB and is just too large)