well, i thought about this the other day...
first of all let me define 'function' - a certain way our consciousness recieves information from our cognitive understanding of the situation. that is, if your functions are Ne, Ti, Fe, and Si, your mind lives in a world portrayed by those structures of information.
now, in this context, the main idea of the shadow functions is that when your under a state of stress - your subjective version of lacking clearity - the information from your main functions are less accessible to you and you end up getting your information from your least conscious and least developed functions.
if we'd have 8 functions, this would mean the 4 functions in the orientation you are not used to having.
but i think the same could be said that if the theory applied to us while have only our 4 functions, a state of mental stress leading us to lack 'clearity', a.k.a. the information we are used to getting, you would have to become reliant on your lesser judging function and lesser percieving function, which means we'd get an opposite order: if your an NT, with T>F and N>S, loosing clearity in your thinking process and intuitve process would leave you to function as an SF, if your an NF, you'd function as an ST.
likewise, if we apply jung's thesis to the 8 function theory - with 4 conscious functions and 4 subconscious functions - he specifically mentions that if your a feeler, your subconscious is a thinker, if your an intuitve, your subconscious would be a sensor. again, if one is lacking clearity and is acting with a lesser degree of consciousness, SFs function as NTs, STs function as NFs.
now, the remaining question can be asked in two forms:
1. we can ask whether we have 8 functions or 4, and we can ask that if we have 4, could stress switch their orientation.
2. we can ask whether we switch our main judgement/perception orientation (j/P) and our main introversion/extroversion orientation (I/E).
the first can be a fascinating debate about the nature of functions, and also a very meaningless one - all the theories would be self sustained based on various definitions. we can explore (and i probably will - the gods know my Ne needs some intellectual wanking), but we have very little to deduct or conclude with.
the second is easier, because we can have answers taken right from our collective experiences (our poor escuse of a test group
):
i know that when most of the introverts i have known are under mental distress, they go further into their shells, like wise, i know about myself, that under stress i go into communication overload - i need to get everything out so i can gain a little bit of clearity. i tend to become even more of a perciever and less goal oriented then otherwise, and most judgers seem to become even more extreme judgers.
does this apply to all?
if so,, then we can conclude that regadless of the answers to the first question, we do maintain our main I/E orientation and our main J/P orientation in times of stress, which brings us to conclude that if we really do loose mental clearity in terms of our functions in times of distress, thus switching our two middle letters and maintaining the first and last, which would result in each function having its opposite orientation and opposite order.
ENTPs- Ne>Ti>Fe>Si
would function under distress as:
ESFPs- Se>Fi>Te>Ni
INFJs - Ni>Fe>Ti>Se
would function under distress as:
ISTJs - Si>Te>Fi>Ne
etc...
conclusion: the answer to question 1 - whether we have 8 functions or 4 functions, doesn't matter.
edit: or rather it can be answered indirectly - and we can conclude that since we maintian our I/E & J/P orientations but not our T/F & N/S orientations, we really do end up obtaining information from the opposite orientation (such as Fe instead of Fi), which means we are functioning as if we have 8 functions, or as if the functions switch orientation, suggesting that one of those is true (depending on the idea of loosing mental clearity under distress). i would further like to suggest that our indevidual sources of distress can be linked to our enneagram type.