Yes, it's called "pilot with a brain".
For most purposes, this presumption is adequately validated by getting the candidate to sit half a dozen PPL exams, plus one more IMCR exam, plus (for those who have an IR) one more IR exam (if FAA IR), plus 10 or so more IR exams (if JAA IR). Plus some flight training.
But seriously, it is actually quite normal during IFR operations to be in IMC. During this time, one might be climbing, or one might also (shock, horror) be descending. If, when descending, one becomes visual with the ground, then one is in a position to do a visual approach.
It's awfully difficult to draft legislation which bans descent during IFR!
The question which one could debate is how low one should go. Going down to what on the UK scene is called "MSA" amounts to a DIY instrument approach with a DH of 1000ft.
Sorry to sound patronising but by writing
Is there really such a glaring loophole in the ANO that allows a private pilot to make up their own DIY approach to an airfield with no IAP and choose their own minima?
you walked straight into that one.
