Meh.
I'd be fine if I don't have to jump through hoops to unlock my favorite characters. In the old days it was a very special thing to have unlockable characters. In fact, that far back they were secret characters and their rarity reflected that.
There are ways to make single-player replayable.... like making it entertaining on its own. Outside of that? Meh. This facilitates multiplayer, which is what matters most.