Mabul Bit
note to self; NEVER do anything important on a public library PC...this will be perpetually edited
I've been neglecting this Mabul piece mostly out of deep, concerted laziness. Also out of the sheer volume of material and ideas I have to present...Also out of rabbinic 'neglect' of my requests for 'concept review'. Hopefully their suggestions, if they are forthcoming, will play into this. Recently I found an essay on Yonah that delivers some ideas similar to how I might use them (I might try and unpack later the parallels of boats, deliverance, destruction, etc, in both narratives), were I to formulate something intelligible about the empirical occurance of the Mabul..which this may or may not be. In addition to there being those who lower themselves to a place where they cannot discern between good and evil (roshoyim), I would offer that perhaps there was a time in a very distant past, where there were many who did not develop into a state within the perview of Good and Evil - beyond judgement in a sense - not "culpable", for certain usages of the term (a consequence of this is that, for the Mabul to affect man, wouldn't necessarily have to be global to be universal; I offer up here the possibility that the Mabul is a regional event). It might have taken different groups different amounts of time and experiences to either fall or rise to such a default state (think of a series of stairs, where one may fall or rise to a landing - or slide down the banister). R. Hirsch in Bereshit discusses the spiritual anthropology of early man - one feature is that pastoral peoples were the first Idolators - not tribal, hunter-gatherers; this is in accord with the "UrMonotheismus" approach to the "Origins of Religion", as well as maybe Rambam on the rise of idolatry, Hilchot Avodah Zara 1:1->. The more culturally/technologically "advanced" societies perhaps experienced a "Rashoyim Stage" before being 'default'.

sudden digression!
"Soul Loss" being not at all a strange idea in shamanistic society, in which ("secularly speaking") humankind has spent 99% of their prehistory...so shamanism perhaps being "PreAdamic". This would make sense if one accepts a position of the 974 generations being actual, along with those who have held Adam as having biological forebearers (consider also that our cousins the non-human Neanderthal, had enough of a spiritual grasp of the cosmos that they buried their dead, and did so with tools, jewelry, etc..some sort of spiritual cognizance might not be bound to the Neshamah level alone). Perhaps Rabbinic/Kabbalistic sources have assigned degrees of "spiritual comprehension" to the NaRaN - Nefesh, Ruach and Neshamah (plus) levels. Maybe "PreAdamic Man" had latent NaRaN, essentially "default" level, and societies contemporary to those in the area of the Mabul manifested Nefesh and Ruach and perhaps Neshamah to degrees not "quite" in fulfillment of their potential - where those in the Mabul region had full NaRaN - and were hense culpable for survival or destruction.

sudden redigression!
There are many sources from Chazzal around the different manners by which HKBH engages the world; according to several very strong sources, Providence may extend over species, but not be utilized over individuals of that species (I"H will add links to these sources later). Maybe this could explain more on the situation of those living outside the region of what could be a regional Mabul. They had lowered over time (through different ways and rates in accord with differing peoples; natural disasters, despotic individuality-crushing regimes, slave states, warfare - all of which flourished to a degree we cannot imagine in the Late Holocene), to a least a moral state beyond direct Providence, beyond where they might be partners in a relationship with HKBH - to a state where standards such as "punishment and reward" no longer apply.
This is not to say they necessarily fell culturally, technologically or economically to a caveman level; the 20th Century can evidence how quickly and easily over a few short years (even moments) very 'advanced' nations and groups of peoples can be twisted to a "Roshoyim Stage" - where people honestly argue that "mob rule" was in such affect that it would excuse their behaviors. For others who do not 'achieve' the Roshoyim level; In a time known to be warlike and filled with despots and natural upheavals, many millions of people over the earth could very well have not had very far to fall (and we could perhaps consider the general body of such tyrranical societies somewhat less culpable than the "Higher Ups", who may have even considered themselves, and so considered by others, to be divine). Their "soul loss" need only be for a short time (the duration of the punishing aspect of the Mabul), overlapping maybe in more or less time in that state than the duration of the Mabul's 'potch'. Perhaps "time" only meant something in regards to those in the "Mabul Zone", as 'human' only meant something regarding them as well. The Mabul regarded meanings; there were those who valued them and those who did not; Roshoyim who were destroyed for willfully disregarding meanings, relationships, etc.
I'm not so sure about that "millions of people" in the last paragraph. Assuming for the moment the validity of the geological time scale, 70,000 plus years ago there were only 10,000 reproducing humans on the whole planet. Maybe there have been other similar episodes since then, but before historiography. Very ancient oral narratives (the Holocene era), abound with epic destructions (online accounts abound, maybe links later).
Following this possible scenario, in the course of time - and most essentially with the dispersion of descendants of those who directly experienced the Mabul and Bavel, etc - the Soul levels of these traumatized people was reinvigorated via with the help of a sort of "spiritual Magen David Adom" (including Shem, Cham and Ever, etc). The peoples had experienced natural destruction and the power of nature before. By recounting The Mabul to them - with its narrative of the consequences of sin and redemption, etc, this "Magen David Adom" of the soul could disseminate new perspectives, etc, so the peoples could really grasp the Mabul in their own experiences - much as we do, but in a way most safe westerners can't imagine. (Those who were "coming up the stairs" to that landing experienced something closer to a Peace Corps intervention, though the 'landing' is the same affective situation for both those who rose, fell or slid to the "Default" level).
Was it really necessary for these Tzelemed peoples to be direct historical descendants of Noach - to learn the value of the historical experience of Noach and his offspring? If one considers humans on the earth in addition to Noach (but with the "soul scenario" above in mind), it doesn't seem imperative. What is imperative is a full, comprehensive, creative and morally culpable human soul. This group of "Relief Workers" would have the skills necessary to teach and elevate them in accord with whatever degree they needed to reach "Tzelem Elokim" stage. Rambam, as understood by Rabbi Nosson Wiesz (at least before the censoring of the linked text), saw Adam haRishon having just such a relationship with Shait (Seth/"Shais"). The actual Rambam he uses, on a full reading (also with selected bits of Jose Faur from "Homo Mysticus"; specific page #'s to follow I"H), could apply here regarding "soul regaining" as the reestablishment of mankind outside the Mabul. Perhaps this is an example of "Min haMabul" - those who were "not there" in a literally sense (also in the slang sense we often use, as in "abnormal" people; even if they had been there, they wouldn't "get it"), were there in some spiritual sense (Rav Hirsh says something very strange and allusive in the end of Parashat Bereshit, 6:7), since that in all of creation which was most fully human was there, and was experienced there, in the destruction of the Roshoyim and the redemption of the Righteous. The world outside the region of the Mabul needed afterward to reattain a state, through whatever means, where the full Tzelem Elokim could be established via "Missionizing", mixing culturally and such with the fully-souled humanity out from the Mabul. Something like a planet in a spiritual "suspended animation", whilst only one region of humanity could have experienced the spiritual event fully, in the spiritual cognitive sense as well as the impact.
Anyways, this proposed 'particularized' experiencing of the Divine engagement in the world has similarities to events later in history. Avraham Avinu was a latter-day individual - here HKBH decided to establish a relationship through a family, and through that family to the world (again, Rav Hirsch from Bereshit through to Lekh Lekha), fluctuations of fulfilled potential followed by a transitional generation, then a generation of destruction. Noach and Sons were perhaps such a "from an individual to the world" scenario. Of course the scenario I present here is the only way this could have been accomplished.

What about this regional Mabul I keep assuming as historical?....
This looks promising, also discussed here, here and here.