Hmmm, if you're doing a Winchester Draft, how would you use Cogwork Librarian? Seems way too OP to be able to take two stacks for it. Maybe a stack and a single card replacement for the second pick? Still could be pretty devastating.
(I ask only because my wife and I Winchester draft out of my cube with some frequency)
I'd think just taking a single extra card would be the way to do it.
It will be interesting to see how they incorporate the rules for a card like that since it will presumably have to be in the Comprehensive Rules which have never included any rules about how drafts work.