Can I use android tablet as a handsfree or headset bluetooth device profile ? Status in 2018

This question is a duplicate of this thread from 2011. I am asking because I suspect android may have been subject to an update or two since then.

My use case is

Old car with aux input

Tablet screwed into the dash

Tablet audio out into the car radio and wired microphone next to the rear view mirror into the tablet.

I want to get in my car and take a call, without taking my phone out of my pockets. I’ve been searching an hour, reading 25 page long forum threads, still no definitive answers and almost all threads are from 2012 or so.

With all the people screwing tablet into their car’s dash, there just has to be a way to do this right ?