How do you handle aesthetics? Sounds like a really fun project but a big challenge, at least for me, would be to make it look pretty and not like a Sunday hack.
Hardware is the biggest challenge and what I assume you are asking about. My first approach was to get a double din computer case, which gives you an aftermarket look. The better option is to go to the junk yard and get a stock head unit and replace the internals. The problem here is finding an LCD that fits the dimensions. Another thing I've been thinking about is using a larger LCD that sticks out of the dash like the Tesla Model 3. Downside here is there is no space for physical buttons which I really like.
Agree, creating something nice is challenging, 3d printings may help but I haven't started it yet, waiting to evaluate different screens first.
I've decided not to dismount the car block but using a phone stand modified for my screen.
It's full of ugly cables, the challenging part was to route a cable from the rear of the car to the front :)