Now I know we all feel differently about Harmony of Despair, but most of the gripes concerned its lack of ingenuity and originality. Imagine if you will, a full fledged, newly constructed game. Imagine HoD + Simons Quest.
My concept would be a massively expansive 2D world with various towns where players could hang out, trade items, buy from shops ect. In between towns would be your typical woods and graveyards where destroying enemies would give you items and exp. Alternate paths would send you to different areas, not unlike OoE. So far, everything follows traditional castlevania format fairly closely. Mansions and smaller castles would be spread across the land, each one being similar to a level in HoD format wise. Each time you would enter one, you would come across gaggles of vampire hunters, spell casters, and monster slayers exploring different sections of the castle for plunder or exp. Alternatively, one could organize mobs to raid through castles. Certain castles would vary in enemy difficulty and strength, minimizing overcrowding, and balancing out difficulty for player levels.
Players could pick classes and customize characters, and pick alignment. Rivaling clans of vampire hunters could potentially duel it out in the middle of a cathedral in glorious 2D.
Certainly a game like this could be created and remain 90% accurate to classic castlevania, other than a few additional gameplay elements, few factors would change.
Oh also, once you got to a high enough level, you would get to enter the massive Dracula's Castle and smite his ass. you can fight him as many times as you want, but there would be few save points in his castle, and he would be exceptionally stronger each time you battled.
Now! Who wants to make it!?