I've driven my car with only enough battery to really power the spark plugs and instruments in the dash (alternator failed and I got jump started). It was manageable even with the heavy steering, although to be fair I was driving max 50kph. Perhaps braking at highway speeds would be challenging.

I also much prefer my phone navigation over the in car system (Android Auto/Apple Carplay would solve this). That said, I wouldn't buy the car GP is suggesting, but I could imagine that if you were price sensitive then you might.

No comment around the older systems, I don't really have the knowledge to agree or disagree there.