Just for the sake of thoroughness... another potential problem with using an offset alone would be a case where a set doesn't mint out at all. If a set sells 50% (or whatever), and then the devs ran an offset, the 50% who minted could be reasonably confident that they got a 100% fair mint, but the next 50% couldn't because the devs would be able to calculate what's coming. Ideally, at this time, what I'm interested in is the 721A +

trustless. But, as you note, it's a challenge. :-)