I'm still not sure why people think we'll be seeing a "council of villains" chances are great ITS NOT GOING TO HAPPEN!...at least not in the way we had all hoped when this series was first announced. However I would love to be proven wrong...
And people please stop responding to Milos' trolling ways at this point he's just being ridiculous.
A council of villains is certainly possible. It'd shave the show's formula up a bit...Jafar , Ursula , Maleficent.... It wouldn't technically gave to be a whole season with the villains in every episode... Just a few of them all together then most other episodes just with one of the villains going about there plan.
I suppose other than those 3.... Pan and Rumple could be a part of it... Or the Gingerbread Witch, The Sanderson Sister witches

, blue fairy (if evil) , stromboli (maybe he's got powers of changing people into animals? They never told the pleasure island/donkey aspect of pinocchios story), Dr. whale/frankenstein, the wicked witch of the west, the snow queen (frozen), or the witch from narnia, Dr. Facilier, the female witch from sword in the stone ( or merlin himself), dracula, the villain from black cauldron, Davy Jones/black beard/long john silver, demon from fantasia , gnome king, hades, villain from emporers new groove, etc... Would all work well on the show... Considering they all could be magical characters
As much as id love to see the non magical villains other than prince john most don't really make sense on this magical based show not as real threats anyway (ring master, lady tremane, cruella, shire khan, all the "hunters" from Tarzan, gaston, to rescuers down under, madame medusa, frollo, mulan villain, ratcliffe , scar etc... Id love to see them try... Especially cruella ... But unless she's trying to skin a humanoid simba to steal some sort of magic... It just really seems pushing it. Crime/drama characters don't seem to fit well in this show.
Maybe after wonderland they do a storybrooke spinoff where belle or whomever can be sheriff... Is handling these people