Are any of them Spider-man or Iron Man villains? Or starring in a current comic? I'm sure we could all name a ton of characters that are no more obscure than Spymaster or, say, Hydro-man, but ultimately there's a reason why some of those characters got picked over others.
That being said, I'd love an Enchantress / Executioner pack, and I'll pick up just about any obscure characters to increase the chances of the ones I'm really interested in being made.
Sure: Madame Masque (who is being used currently in a big way) is an Iron Man villain. White Rabbit (also being used) is appearing in both Dark Reign: Mister Negative and will be appearing in the main Spidey series in the upcoming issues. There's also Calypso (would work great with a Kraven 2-pack), who is pretty iconic. Titania is probably the most prominent of street-level female villains and is a longtime Spidey foe. I'm still shocked she nor Volcana were options in the Secret Wars poll, since they both played large roles.
Maybe a Thor-themed four pack will be released one day with Enchantress & Executioner. And maybe She-Loki!