I hope nobody minds that I open a new thread for this.
I just flashed my Android L / 5.0 Image without the Radio from here
. After initial Setup I installed rSap with the installation files, rebooted and went to my car and tested it. Voila, works out of the box. So there is hope for N5 users who want to update.
I will keep reporting my experience here for others to follow.
I even noticed one improovement: With Andoid 4.4.4 (Stock+Root) I always came to the networkprovider selection screen, although I already hat good reception. I don't have that now.
On my way home this afternoon I will test some more things including phonebook and WLAN.UPDATE
On my way home from work I managed to play a bit with my setup. It's incredible, everything works flawless. From Connecting, making calls, (updating) phonebook and dialing from it. Awesome.
One more advantage of Andoid L ist that you can hide the "always active" notification from rsap in the notification bar.
Whoever wants to know my Setup:
Nexus 5 16GB
VW Golf 5
3C8 035 730D (rSAP, HFP, WLAN)
MFA black/white Instrumentcluster from recent Scirocco