I guess I overlooked it because the other way is so logically trivial, since it basically boils down to A -> B => (A || Nothing) -> B, which is just an or-introduction. So if you wanna implement Maybe generically the "work" lies on the other side.

But since Hickey's argument sort of is that we shouldn't implement Maybe generically, I guess my argument here becomes circular. (Begging the question maybe?)

Yeah, that's (part of) Hickey's point. That the "best" type systems fail this test, and require manual programmer work to solve this problem. Again, I'm saying this as someone who really appreciates Haskell.