PFR - they already are! There are very stringent rules for certification of all pilots.

When I flew gliders, we had a very highly experienced pilot who was not permitted to fly solo because of health issues - I forget exactly what they were, it was a good many years ago, but it meant that every flight had to be in a two-.seater with another qualified pilot in the other seat.

And, of course, it wasn't an 'older and vintage pilot' who flew the Germanwings Airbus into the mountainside recently!