Yes I was asking for feedback. I like thinking and talking about these kind of things. A little warning though, when it comes down to Dominion cards, all you and I can do is have opinions and reasoning, but in the end only one opinion will actually count (Donalds).
I don't really like hiding the contents. The most fun part in Black Market for me is figuring out if it's worth going for it. If you hide the contents, you kind of have to go for it every time, and I really don't like cards that you have to go for most of the time. Also not sure as well how you would hide the contents with cards in it that add extra piles or the Baker token for that matter.
Also for the same reasoning, you kind of have to go for Black Market if there is every card in it which ruins the fun of figuring out if it's worth going for it.
While you have some valid points, here are some more thoughts in kind of random order:
1) If you put all cards in the Black Market deck (the way the card was designed to), your game probably sees only the top 30-or-so. If both players go heavy engine maybe the top 100. There is no functional difference between a card not being in the black market deck, and a card being below the top-X anyway, where X is the number of cards your game reveals. (except for setup)
2) Your decision to go for the Black Market or not should not depend on its content, period. This has nothing to do with card or program design, just some strategical advice. Look at the rest of the kingdom; if you can build an engine go for Black Market - always.
3) The 25-cards-in-BM was not invented by Donald. Isotropic had it, goko probably assumed that's how it was supposed to work, but it simply doesn't state that on the card. Donald never really cared enough to do something about it, it's only a promo anyway.
4) Putting all cards in the BM is a bit awkward for setup rules indeed. I wouldn't mind always getting an extra pile (YW) or a coin token (baker) but always doing all the setup... hmmm.
5) Putting all cards in the BM might turn out to be too much for clients that don't like loading all the images (say, on a phone with a lousy internet connection). A bit soon to tell though.
6) In the current implementation the combination of full-game-log and a recycling small black market deck implies that on the second cycle you can know exactly what shows up, if you are willing to invest (waste) the time on it. Regardless of what else, I want to stop that.
7) While you may enjoy reading through all the black market deck cards at the start of the game, there is a reasonable chance your opponent doesn't enjoy the wait.