This will sound absolutely mental but:
A remake of Simon's Quest with a lot of (too ambitious 

) additions. 
Imagine it, a 3D Open world, where you can decide how to tackle the count: 
-Players can take the linear root, find Dracula's parts in separate dungeons, and go straight for the count himself
- Optional side-quests that add to a karma rating,as at this time, the Belmonts were feared by the general public. If you gain enough trust, you can build an army to help fight the count and make things much easier. Of course if you don't do any quests, the villagers will give you the infamously misleading clues from the NES game.
-You can choose not to fight the count at all, and go on 3 other alternate quests with completely different items to collect, some easier, some harder: Cure Simon's illness, revive Alucard to help you or even become Dracula yourself (yes, like LOS, and yes, assuming Legends is canon)
- Maybe 20 in-game days to complete the game, perhaps it could be an optional mode? It did become a little annoying in CV64 afterall
Maybe not everyone's cup of tea, but I think it would be an interesting game. 
Otherwise, another classicvania, or reviving one of the cancelled games: Castlevania:Resurrection or Castlevania:Bloodletting?