My question is, can someone of 70 ever be a truly 'natural' pilot? Will they be able to develop the motor skills so that controlling the aeroplane accurately becomes second nature, not something that needs to be thought about?
Does that really matter?
No, I don't think a 70-year old will be able to develop the motor skills that we generally see in fighter pilots. But I don't think it's going to be necessary. At that age, I can imagine that learning to fly is something someone wants to do before he dies. Or something along those lines. If that means learning to fly, and eventually fly, in benign conditions, in a docile aircraft with plenty time to think about your actions, why not?
At that age, I don't think somebody would be continuing on with fighter training, aerobatics, instrument ratings, tailwheel, commercial flying and so forth anyway.
(Edited: WTF is wrong with PPRuNe today that it puts my answer as #1, with the question as #2???)