What I need the most is the music.
I liked everything about previous games (yes, anime style also). The exploration and completion of maps (even on the 3D entries of the saga), the leveling up, equipping armors, weapons, magic...
But what I really, REALLY MISS, and I mean, A LOT, is the music. Be it Michiru Yamane or other composer from previous games, which all did a wonderful soundtrack, or someone new doing the same style of music (I'm thinking right now of "Dusk Falls" by Jake Kaufman, from Bloodrayne, or some themes from Bayonetta, like "One of a kind").
Of course it's just my opinion, but I believe that Castlevania, without its characteristic music, is not Castlevania.
Just for making an example... Imagine an old school Megaman with Hollywood music...
Well, for me it's the same.
But it's not just the music, just for the record.
I don't want to buy combos, I want to buy new equipment, items, spells...
And I like female lead characters, which in this sort of game looks like never happens (but could be a possibility with WayForward or Platinum).
And I don't have anything against 2.5D gameplay, but at least to me, there's nothing like good old sprites, especially for portable games.
I wouldn't object a 3D game with realistic graphics, always if it has the atmosphere and look of Castlevania, but I need the rest of things I said.
All this I say with respect, of course, but it's just the way I feel.
I really, really lawn for a new Castlevania like those back in the old (and not so old) days.