Hi Jan,
I am nothing if not a nitpicky twat. I am not sure if you will take my pointing out the contradictions in what you are looking for as a service or a distraction, but here goes.
Jan Pavuk:
Word "hardcore" is used as D. Ingram often uses his concept of "core teachings of the Buddha". (It has little to do with how long one sits.)
Not sure that that is how Daniel uses the word "hardcore", or whether it is a good definition to begin with, but if that is how you define the word, I will play along for the discussion at hand.
The problem with this definition is that different people have very different ideas about what Gautama originally taught. Scholars agree that the majority of the Pali Canon was written by other people than Gautama, and tend to disagree on what exactly in the Pali Canon is originally his teaching. So there is no way of knowing what the core teachings of the Buddha
actually were... although Daniel's interpretation is extremely useful in practice, much of what he talks about is not in the Pali Canon. (And, again, much of what is in the Pali Canon is not Gautama's original teachings anyway.)
There is also obviously a contradiction between the fact that you say that you want something that is "the core teachings of the Buddha", and the passage that you quoted from MCTB, which says "purely secular, utterly devoid of any explicit reference to any ancient frameworks, totally scrubbed of anything religious, and free of any term that is in any way alien to the predominant linguistic sensibilities in the area of the world where I reside".
Jan Pavuk:
a good teacher would be a pragmatic agnostic with deep personal knowledge of training techniques in attention/concentration and perception/peripheral awarenessteacher would be highly skilled in (or at least knowledgable of) techniques from several mystic traditions, but also from other fields where expectional attention and awareness is needed (think pilots, sports, warriors, etc.) So, TMI. That distinction between attention and peripheral awareness, and the emphasis on that, is a (very interesting and useful) innovation by Culadasa. It is not in the Pali Canon. It is not a bad thing (just like it is not a bad thing that MCTB is probably not actually the original teachings of the Buddha).
Also, you are probably aware of the very deep disagreements between Daniel and Culadasa on the ñanas and what the Buddha originally taught.
So I guess that the TL;DR is that if you want to practice the Buddha's Original Teachings™, you will need to become a scholar of Pali, Sanskrit, Chinese, and Buddhist philology, read the old texts, and come to your own conclusions about what those were, which will most likely be "we don't know". It sounds like a big detour to me.