Thank you very much for the comprehensive report on your project. I had been searching for a solution for my 2013 IS350 F-Sport. It only has 46,000kms on it so I'd like to keep it for many more years and the only issue I had was the ridiculous cost for an update of maps for the OEM system. The link you have provided is extremely promising.
Just sharing this in case someone is interested.
I installed an Android Auto / Apple CarPlay kit on my 2012 IS350.
It is not cheap, but I like my car and I wanted to have updated maps.
I did the installation myself; I deviated a little bit from the supplied instructions.
I used a DNA USB adaptor instead of the supplied one as I didn’t want to drill a new hole.
I also modified slightly the microphone to make it fit in a blank button cover.
This supports wired or wireless connectivity.
I have been using it since February connecting my Pixel phone.
The system is 100% stable; it always connects on the first attempt and responds quickly.
A long press on the hangup steering wheel button toggles between OEM and the kit.
I had an audio issue which I found a solution for.
Their support generally responds quickly.
I would rate this 9.5 out of 10.
I have nothing to do with the company that sell this; I am just sharing it as someone might be looking for options.
These are the links: