Impossible questions CS. Whatever might be acceptable to cut in the operation of a piston-engine aircraft or turboprop aircraft may not be acceptable in a jet. In any event, I tend to agree with Cathar and lomapaseo - the minimum standard in everything is the rule book, whatever your aviation regulator defines that to be.
And I stress "minimum standard". I suspect that there are a few circumstances where I'd be getting worried long before we reach that "minimum standard". However, that is what your regulator looks at, tho they ARE entitled to assess any company on their own standards, as written in Ops Manuals, SOPs, etc., where these are higher than those in the rule book.
The real point is not whether the regulator has the power, but whether or not they can (or are willing to) enforce their own regulations.