I could be on board with Luke saying mostly to himself and with a smile, "When 900 years old you reach look as good you will not." Remembering Yoda's words, having that sense of humor/humility and recognizing his Yoda-like status would be good. It would be less about admitting infirmity but recognizing what youth meant - something plenty of us non-octogenarian fans have been learning. It could show that kind of reflection.

Getting in shape is for general appearances as well as physical action I imagine.

I was thinking Benedict Cumberbatch would be a compelling son of Tarkin, but I agree we shouldn't go much in that direction. In my fantasy world, Cumberbatch would have played Doctor Who and instead of Star Trek would have some role in Star Wars.