AAuto won't help as AAutomotive doesn't support it. Just run Amazon Music on Android and stream over BT. The only drawback is folder control and album art are missing right now. Will be fixed with AAutomotive 11.
My bet would be at least another 6 months until AA11. At least we are now being upgraded to the same platform as the XC40E. That should allow the devs to focus on one platform.