Other way around. If you are going to set up the paradigm you (and MBTI) have proposed you actually need to expand the types not narrow them down. Because what happens is you don't allow for a non-structured INFP for example. MBTI simply says that if you are a P you must be non-structured and J must be structured and does not allow for the possibility that a Ni-dom might prefer to be P-like (all Ni-doms must be J's in MBTI). So we actually have to devise a nomenclature that allows for types to be both closure seeking and non-closure seeking. Because its a little silly to say that ESFPs with their tertiary Te will always be non-closure seeking, surely a closure-seeking ESFP or ENFP exists.I was thinking (sometimes dangerous being an INFP, I'm aware ) and I thought if they only use to have 3 letters for each function (e.g INF, EST, INT, etc) and then they added one on after (which is literally just do you see the possibilites and stay opened minded or do you form judgements and stay structered) then perhaps there is an opputunity to create yet another function/letter to narrow down types even more.
By the way Fudjack and Dinkelaker did exactly what you are proposing and came up with a nomenclature to allow for this What We Mean When We Speak of the 'inFp', etc - A Critique of the J/P Designation in the MBTI