On the age front, you can’t measure this in any objective other way but the date on your birth certificate. If you want to develop a telemere based measurement, fine - but these biological age based markers are all influenced by exercise, which might defeat whatever classification you’d be trying to achieve anyway.
Sex isn’t as clear-cut as you make it sound. I know we were all taught about XX and XY in school but its far more complicated than that. So what about XXY? Or those with androgen insensitivity syndrome - those who are XY but cannot process testosterone and therefore outwardly appear and be labelled at birth as female? Obviously we’re not going to do DNA tests before every turkey trot.
My point is that sex and gender are both far from clear cut, no matter how you slice it. Age, on the other hand, is a very clear and objective measurement.
If we’re taking about edge cases for biological sex then I suggest we do the same thing we do with ages. Generally age in sport is whatever you’re age will be on Dec 31 or Jan 01 of that year. That means sometimes your cooking against someone 364 days older than you. Draw a line in the sand for biological sex. CAS screwed up with their Semenya ruling, but at least they gave a measurable metric by which one could be included.
I disagree with you that biological sex is not clear cut. Everything in the real world is a shade of gray, but biological sex is a very very dark (or light) gray. For >>>99% of people a non-biased clinical assessment can be made of they are naturally male or female.