So I tried to find which Darkstalkers characters have been on Nintendo consoles, and most of them seem to just come from both Project X Zone games: Morrigan (also playable in Tatsunoko vs Capcom), Felicia, Hsien-Ko, Demitri (as playable characters), Lord Raptor, Jedah, Q-Bee, B. B. Hood and Pyron (as enemy units). Lilith also makes a cameo in Tatsunoko vs Capcom during Morrigan's Darkness Illusion hyper.
Now, my main issue with these guys is that all suffer from one problem or another that could potentially prevent them from joining: All girls minus B.B.Hood would have to be toned down in their outfits, Q-Bee is a generic enemy, Demitri would lack his (in)famous Midnight Bliss attack (which is why he was rejected from MvC3, according to Niitsuma), and all the other guys aren't just well-known enough.
I'd love to have a character from that franchise in the game if only because wacky animations don't seem to be a problem here (lookin' at 'ya, Corrin), but I feel like it'd only happen if Capcom themselves stepped in.