I will repeat that your suggestion about using a couple of nuts (equalised with whatever material) and using them to 'protect' the move on BS is NOT best practise and never will be - for reasons you are saying don't apply in this situation.
Just out of interest I have phoned a couple of my friends, both MIC's, who agree with my statement that the safe ways to 'climb' BS are either to lead it with leader placed protection. To top-rope it or to bottom rope it. Or indeed for a COMPETANT person to solo it.
I understand what you are saying about this exact scenario and the set-up you use and whilst it SHOULD be fine to use what I am saying is that it is not best practise and is not a good idea in my eyes and those of 2 other qualified Mountain Instructors. Indeed if you suggested using your set-up in a Mountain Instructors assessment you would not be passing.
I understand your posistion and now I hope you understand mine. I am not proporting to be some holier than tho type where everything must always ,and only ,be done by the book.