Ok, I completely focussed on the hands that lost the least equity when 3betted compaired to playing against a 50% preflop opening range, while being smashed against 4bets.
Pretty much what became obvious that pairs bigger than 77 and high cards would perform much better against the 50% range, as against the defend range. Especially Ace highs had too much value passively defended and even at least the suited ones performed nearly as good vs the defending range as the 4bet range.
So it quickly became transparent that suited compared to offsuit low cards and low pairs would suffer the least equity loss playing against a defending range, while giving them up against a 4bet while playing worse against 50% opening due to much better low board coverage from BU.
Now it was all about judging gappers vs connectors in terms of their playability and equity against 50% vs 3bet defend. Again it seemed that gappers seem to be less equity loss struck than connectors, only if you went down to 32s you would experience a gapper like behaviour in terms of equity.
So my 3bet bluffing range, giving all the parameters (50% pfr, defend range: TT-22,AQs-A2s,K8s+,QTs+,J9s+,T8s+,97s+,87s,76s,AQo-ATo,KJo+, 4bet range: JJ+,AKs,AKo) would look like this:
77-22,74s+,62s+,52s+,42s+,32s (6.64% of hands total)
When we remember that we need 20% equity at least against the defending range in order to achieve neutral ev, this is how we look like against BU defend range:
This range overall only loses ~2.6% equity compared to facing a 50% PFR range:
While getting smashed against the 4bet range:
If you would have to get a little less bluff heavy (6.6% is a lot), the hands to deduct would be the hands that would get the least crushed against the 4bet range, while being equally good against the other two ranges, which obviously would be the pairs:
But deducting all pairs would mean getting down to 4% overall, which might make our 3betting range overall become too nutted and allowing BTN to defend tighter ranges against our overall frequency. So in order to get the "bluff" segment up we would start adding pairs starting with deuces up to fives and even up to 77 if BU really defends a wide standard range.
Another thing that became quite apparent was that we cover low boards much much better than the buttons defend range. Meaning we either flop overcard equity, a pair or an overpair with our entire range and put BU in a ton of ugly spots.
I hope this was what you were looking for Simon.