can you please state exactly what you mean by 'asymetric ranges'? you use the term as if it's standard, but i've never heard it and i've been a winning mid-stakes grinder for a while now.
(ok now i see you already answered that. but the term 'asymetric' seems a bit misleading to me, suggests other meaning apart from just one range being stronger than the other. is that really exactly what you mean by 'asymetric'? x and y are symetric generally means more than one metric of the relata, e.g. strength, is equal. it usually says something about the arrangement/shape/structure of the relata)
also what does '1-a' mean?
in your first example, BU flatting CO OR and low, dry flop, why do you assume that CO preflop range is much stronger than BU? CO probably has about 30%, maybe 35%, BU will be folding a lot of hands out of those 30% and can be flat-calling the top of his range at an unknown frequency. not only that, but some of the marginal hands that miss this flop will be put in BU's 3bet range and thus removed from his flatting range. (btw, question: what % do you think BU should defend vs 30% CO open, total of flats+3bets?)
on this particular board texture i think i do agree with what you're saying, at least the way i interpreted it: problem with this board is that theres just not going to by a strong range we can represent on any turn/river (except if turn is 3 and river is 5 or something like that). now there are various ways of reacting to this and manipulating perceived ranges of various lines, but i don't want to get into those details.
imo overall we should just over-fold this flop and see it as a correct reaction to negative variance: this is simply an unlucky flop given preflop ranges
that being said, maybe that's not necessary at all, because a) we have position and b)our range isn't actually much weaker than CO (of course depends on our exact preflop strategy)