It all seems quite simple to me really
An therein lies the problem AF - life is seldom simple, and simple policies seldom work.
As has already been pointed out - Mr Bader and his 22 aerial victories would have fallen foul of your interpretion. and if you think that example somewhat singular and over-used, how about the rather talented one-legged AEO that served with distinction (is he still in by the way). I'm sure others can think of other examples.
That's the problem with the one solution fits all. Yes, out go the lazy, feckless and grossly unfit (funny thing, as a flight commander I could identify those and take the appropriate action, without any help from the PED staff whatsoever.)
Out also go many talented, hard-working and well-motivated individuals, on the grounds that, for some reason, they don't fit some arbitary PEd inspired assessment of "fitness".
You like simple...here's simple
Let the medical staff decide if you are healthy enough for military service and healthy enough for any extra requirements (flying, diving etc).
Let the command chain report on your performance, standards, bearing etc.
Promote, demote, administrate as necessary.