I do have this situation, I have a custom template that's got additional 'no code' items, one of which is the non-conformity with BS7671 not having an effect on safety and where improvement is not specifically recommended. Strictly speaking such issues don't have to be reported (so it follows they cant be coded) but noting them as no code proves you have seen and assessed them. I'd use it for plastic combustible consumer unit not on the escape route, if you say C3 then you are recommending its replaced, many cases such a recommendation could not be justified, but should you make no reference to it bearing in mind there s a specific field on section of inspections for it, it clearly cant be ticked and its not NA or lim so you need to point to something explaining the situation.
So yes we do need C3 and C4 IMHO