Shortly after I got my driving license, we went to Tuscany on holiday.
My parents, who we were visiting, thought it would be good for me to learn to drive on the right, too, so they let me drive their car, a Fiat Multipla.
One feature of that car is that it has split wing mirrors (see the photo): The top part is a normal wing mirror, while the bottom part is fixed to show the bottom edge of the car.
It’s probably designed to make parking easier (and it definitely works for that purpose), but I found it invaluable to learn to gauge the width of the car.
Basically, at first I had no idea where the edge of the road was, but once I learned to check the bottom mirror, I found I could see precisely where I was.
I probably only used it intensively for an hour or two, and I then got a really good feel for the width of the car.
Actually, when I returned to the UK, I realised that I actually felt less able to gauge the width of my own car.
It’s not really the kind of thing you need all the time, but it would be a wonderful feature every time you drive a new car.