You seem to forget that Grandpas have rights, for example to live their life, and. being able to get from A to B is part of that.

FSD does not have rights.

Once grandpa's vision, reaction time, etc. declines to the point he becomes unsafe he should be losing his license anyways. That's the law today, though it is not enforced as strictly as it should be. In my model grandpa maintains the ability to travel by using FSD and everyone is safer, in your model he loses his license and is stuck at home or more people die.

Which is why many countries have a 18 year limit for driving, plus in my country there are people pushing for mandatory regular driving tests for old people.

If FSD is statistically safer than the 18 year old (or new driver of any age), is it ethical to knowingly cause more death by forcing the new driver to drive instead of allowing them to use FSD?