As I understand it Melchy, you must be fit or, undergoing (limited) remedial or, exempted or you are out! Therefore, I do not follow your comment on a promotion tick-box as everyone is compliant.
However, I do agree that a structured system of fitness levels for "the job" would be a way forward and, that would be finite levels, regardless of gender.
The present system smacks of empire building and manipulation of personel. As for lifestyle choice well, I think "choice" (within the service requirements) is the word here.
Cheers
OAP