I would use a different approach if I was Google. By default all apps are blocked only ones in whitelist will work, whitelist is server side, aka game over for any errors party app.Sure but using AA 2.9 won't work for ever.
Basically it's a cat and mouse game now. Google will always have a better way to block the apps, since they are in total control of the AA apk and Play services.
The holy grail would be - as someone said before - to transmit audio and video to the AA head unit by using a completely different app. But this is probably very hard.
And that indian YouTube moron is still keeping his blog and apk downloads online which will probably make Google search for a better way to block.. Probably the next step is to block v. 2.9 in Playservices. This is possible easily as you can try to revert to a really old AA version - that won't run on latest playservices.
Creating a replacement AA is well.... Uhhhhh there are so many challenges with it...
As a first off you need to be able to do an SSL handshake with the headunit and you need to be able to react to all the things in the correct way, more or less this is dines but in opposite direction in HUR. Then you need to write an app which can capture screen on android and inject touch events and so on, which is either a root app either a system app. Potentially you can mock up something with accessibility services but that is also getting reviewed and closed by Google. So easier sad then done. Then you need to find a way to make your app still capture screen even when the device goes in standby and the screen is off, otherwise you will put too much pressure on the battery of the phone if screen is always on. Yeah sure it can be done but not healthy for battery. In a nutshell I think it's too much work and beside that will really unleash all the wrong potentials... I know you can buy an android powered headunit and have it fully unlocked but I wouldn't like to add another way to having distracted users while driving (I was one of them in the past with age you tend to see things differently....)