A Vanillaware Castlevania game would look awesome, but as others stated, the gameplay might be more RPG (walking back and forth) and beat em up - afterall, the guy behind all the Vanillaware game started off being involved in the Capcom Dungeons and Dragons games, which Dragon's Crown is considered a spiritual Sequel to.
How about Arc Systems and Wayforward? I think the former would be innovative, but would be filled with an exaggerated anime art style with a heavy metal soundtrack. If one could over the art style, the game would probably be good. As for Wayforward, I would imagine them making a CV sequel more like a remake of the first Castlevania game, but with a few elements thrown in. One of the things I do not like about Contra 4 is that the gameplay feels too dependent on nostalgia with the first half of the game being based on Contra 1 with an ability of Bionic Commando thrown in. I had fun playing their Ducktales remake, but that, of course is a remake of a classic Capcom game. Then again, Castlevania games of the past heavily used stages and boss battles from other Castlevania games, so that might work for CV.