Sometimes drivers use one number during their junior days but then cannot use it because it's taken. When the other driver retires, why not try to get that number?

In order for this to be discussed, surely there must be already at least one case of a driver who wants to change his number

I mean, better a minimum of 55 per cent of the car’s surface area (when viewed from the side and above) must be covered in either painted or stickered liveries, than no rule on that at all and the FIA deciding on "vibes".