The Role of Normative Supremeness, the section you read, is part of the Book of Instruments, a mainly philosophical book which, in turn, is part of the Model of Neutral-Inclusivity, a major philosophical-denominational work. The doctrine introduced and defended in the Model is not theistic or atheistic in any conventional sense: it is, first and foremost, normistic, that is, based on the primacy of norms and values (rather than on that of gods and/or demons in the singular or plural). The values considered fundamental in the Model are truth, relevance/inclusivity, (catenical) neutrality and personhood. The Model was first published on paper 41 years after the Second World War. Its publication on the Internet started 9 years later and continues until the present day.
    The acronym TRINP for TRuth, Relevance, Inclusiveness, Neutrality and Personhood does not occur in the Model of Neutral-Inclusivity, but was used for the first time on InSite. InSite is the original name of the website which received its present name TRINPsite 7 years ago. You should visit the main document at http://www.trinp.org/MainDoc.htm and the main index page at http://www.trinp.org/index.htm and the pages linked to from there for more of this kind of information.
    From a normistic point of view a person cannot justifiably be interested in (a) supreme being/being supreme without being interested in norms and values above all. It is only theocentrists (theists and atheists alike) who fight about such a matter as the (non)existence of God/gods or (a) supreme being, while forgetting what it is that makes something better or worse in the first place, regardless of the (non)existence of any god, demon or supreme being. Therefore i strongly advise you to study the question of denominational primacy in the Model. The fourth division of the sixth chapter of the Book of Fundamentals (http://www.trinp.org/MNI/BoF/6/4.htm) deals with this issue in particular.
    As far as the concept of supreme being itself is concerned, it might also be worthwhile for you to read (parts of) the third chapter of the Book of Symbols, especially the section on 'the truth and relevancy of [the supreme being's] existence' (http://www.trinp.org/MNI/BoS/3/1/4.HTM). Note that truth here means truth and/or falsehood and that relevancy here means relevance and/or irrelevance.
    I hope i have answered your questions of how and where TRINP originated. The answer to your question of why it originated cannot be equally simple and concrete, i fear. May i venture to reply that the explicit recognition of the TRINP values was bound to come about in a world replete with supernaturalism, exclusivism and extremism?

You will have noticed that the term inclusivity does not (yet) occur in traditional paper dictionaries, whereas the term exclusivity has been recognized by everyone as a (near-)synonym of exclusiveness. It is no wonder, then, that purely on the basis of the analogy inclusivity had to and did come into existence somewhere sometime.
    The earliest use of the term inclusivity i know of is in the manuscripts and typescripts which preceded the Model of Neutral-Inclusivity by Vinsent Nandi (see www.trinp.org/MNI/MainDoc.htm) --if i am not mistaken in those parts which were written 25 to 30 years after the Second World War. The Model was published 41 years aSWW, so you may prefer that year as the 'official' one.
    There was a special reason for introducing the concept of inclusivity in the Model of Neutral-Inclusivity. It is a much wider notion than inclusive thought, for instance, covering not only the cognitive but also the affective and conative aspects of people's attitudes; not only thought but also action. With the stress put on the unity of thinking, feeling and acting a clear distinction between the inclusive and the exclusive attitude emerged; between exclusion and exclusivity on the one hand and inclusion and inclusivity on the other. Inclusivity then becomes the complete opposite of exclusivist acts, practices and teachings, inclusive of those created, perpetuated and/or promoted by the Bible and the Koran.
    Should you be interested in the substance too, you are especially advised to read the first two chapters of the second Model book, the Book of Fundamentals. (Address: www.trinp.org/MNI/BoF.htm.) It is in the very first section of this book where --apart from the title of the Model-- the term inclusivity appears for the first time.

I am sorry to inform you that i do not have, nor know of, any literal translation of the Middle Dutch play Elckerlijc (=Elckerlyc). As i speak Dutch myself, i have not been looking for one.
    However, i think i can answer your question whether the debate on priesthood between Knowledge and Five Wits in the Middle Dutch (or 'Flemish') Elckerlijc is similar to the English Everyman, for it certainly is. 'Similar' must, then, be understood in the same way as for the rest of the play. It definitely is not a completely literal translation, if only because it was necessary to change words or the order of words for the respective rime schemes in Dutch and English.
    I have a copy of Elckerlijc and Everyman printed together on the left and right pages. In this copy the debate on priesthood runs in Everyman from line 706 ("Everyman, harken what I say:") to line 770 ("Which hath made true satisfaction."), while in Elckerlijc it runs from line 660 to line 725: 65 lines in both versions. The greatest deviation seems to be in the last three lines, where Vijf Sinnen says in Elckerlijc:
"We are their [=the priests'] sheep and they our shepherds, /
  By whom all of us are protected, /
  Let's not talk about it anymore."
Other deviations are much smaller or, i believe, insignificant, as far as contents are concerned.

When you write that you are 'indifferent to everything on, in and around this planet' i do not know how to interpret this. It could mean 'not interested in' and 'not committed to anything', which i would regret. Yet, you continue with wondering what life would be like if you 'possessed knowledge of what is truth and what is not truth'. From this i take it that you recognize at least truth as something good in itself.
    As far as truth is concerned, this is what you should do with your life: do not lie and do not break a promise (or even a threat), neither to others nor to yourself. You will respect truth by not lying about a cookie you may have stolen from a biscuit tin, but in general you respect truth by not claiming or saying anything for which you have no evidence or logical proof. Therefore you should resist all forms of supernaturalism, whether of the institutionalized sort (as in a church or mosque) or not.
    However, truth is only one value among several. And the recognition of truth in isolation will merely make you a victim of irrelevantism. There is so much more to life! Visit TRINPsite (www.trinp.org) and see for yourself what the acronym TRINP stands for. It stands for no fewer than five values (four ultimate ones): TRuth, Relevance, INclusiveness, Neutrality and Personhood.
    Should you not want to or not be able to read the Model of Neutral-Inclusivity from beginning to end, you could start with the parts of the Model linked to from the respective Value documents (www.trinp.org/Valu/Tru.htm for truth, etc). Try to understand at least these parts of the Model and you will never need to ask me or anyone else anymore what a person could do with 'er life. You will only have to ask yourself what you could do in your particular circumstances with your particular capacities to improve yourself and/or the world of which you are part, if not in the short then in the long term, alone or with others.
    May TRINPsite inform and inspire you.

I will try to answer your three questions.
    TRINPsite is mainly based on the Model of Neutral-Inclusivity and this work might be called "an attempt at consolidating a belief system", as you put it. It is also --to use your words again-- very 'structured'. I do not know how to interpret your phrase 'systems in their most high structured truths and relevances', and therefore i must forgo dealing with this part of your first question.
    As to your second question: neither the path of knowing nor the path of not knowing is the real discipline. The real discipline lies in solely claiming what is justified belief and not claiming what you cannot or do not know. Knowledge nor ignorance is an ultimate value in itself, but truth is. You do not only respect the truth by not telling falsehoods but also by not affirming or denying anything you do not know. This is precisely why supernaturalist claims, like ordinary lies, are objectionable. But do not believe and say that we do not and cannot know anything at all, for then it would not even have made sense for you to ask your questions and for me to write this reply. The Book of Instruments of the Model of Neutral-Inclusivity is not only very clear about the value and interpretation of truth but also about the value and interpretation of relevance. Unlike truth, relevance is a relational notion: something is not (ir)relevant in some absolute sense but always with regard to a certain goal.
    So, when you ask me if a consolidated and structured system is not faulty in relevance to a degree, i cannot answer your question in general, since it depends on the (your?my?) objectives. Yet, as far as TRINPsite and the Model are concerned, i will be so bold as to answer you. The Model does certainly and most willingly 'consolidate' relevance and truth and a limited number of other values in a very structured way. It is precisely because of its enforcement and reinforcement of relevance as a value that it would be absurd to accuse it of being faulty in relevance, especially where and when it surpasses any specific focus of relevancy. You must realize that you yourself in your formulation of your question implicitly treat relevance as a value too. And, indeed, it is: the second of the TRINP values.
    Should i not have answered your questions exactly and completely (which, i fear, i have not), i hope i have at least made it worthwhile for you to pose them.

With regard to your question i must inform you that the Model of Neutral-Inclusivity (consisting of three Books) was already published on paper more than 15 years ago. (See www.trinp.org/MNI/MainDoc.htm for further details.)
    I don't know how much you've read of the Model, but one of the last ones you would expect to accept this denominational-philosophical work is an established publisher from an era dominated by religion and some wishy-washy humanism or anemic atheism on the fringe. Therefore, it was never offered to such a publisher. Instead, it was first published on paper privately and since that drew hardly any attention, it was republished and will continue to be republished on the Internet, where it is now drawing an ever-increasing number of visitors and, presumably, readers.
    You seem to suggest that the acceptance of a book depends on its publication in print, and in the short run and from a traditional point of view you may be right. However, in the long run such a publication does not prove anything in itself. The Model is a work of reason and in the realm of reason it is not the authority of a publisher, nor of a writer, that counts, but the long-term validity of arguments. And i venture to believe that eventually new sense will prevail over old nonsense, especially when i'm getting encouraging comments like yours.

TRINP: Truth, Relevance, Inclusiveness, (Catenical) Neutrality and Personhood.
    See TRINPsite.