Ditch the first game's artstyle and the ridiculous time travel nonsense. Matter of fact, retcon the first game entirely...don't even call this one Judgement 2.
I say a better story set up would be to have Dracula or Chaos or Death...or all of the above...somehow anchor the souls of all heroes that ventured into Castlevania to the keep itself (perhaps a persistent curse???). Then have the game take place in the dark alternate realm where Castlevania exists between games (after our heroes have moved on from this world). Have Dracula pit all of his former opponents against each other with the prize for victory being an open door out of his eternal purgatory....back to heaven. Of course, some of Dracula's henchmen could also be in attendance...for added challenge (or for their own reasons).
The first game's roster is solid for the most part, they just need to pretty much all be redesigned (and give Eric his manhood back for gods sake). In addition:
*Richter Belmont
*Shaft
*Olrox
*Medusa
*Isaac (I welcome any opportunity to beat that guy down again)
*Skeleton Knight
*Minotaur
*Frankenstein's Monster
*Sonia Belmont
Now that I'm thinking about it, how about offering a glorified Boss Rush mode featuring fights with some of the series' best boss characters? Maybe offer equipment unlockables as prizes for achieving certain feats during the game (or let us purchase them via an ingame merchant using gold earned during fights or challenges). A full fledged character customization tool would be sweet too.
Oh, and I forgot one last thing.......DON'T let anyone that made the first game work on it. It's no problem to take some of those elements in the original that worked into the sequel/reboot, but after spending numerious hours trying to enjoy Judgement I came to the conclusion that the team responsible for it just didn't have a very solid grasp of how to execute their vision for it.