I wouldn't mind a "Castlevania Collection" released on the Vita, in volumes.
Volume I would feature "HD" remasters of Castlevania I-III
Volume II would feature "HD" remasters of Super Castlevania IV and Dracula X Chronicles (featuring the unlockable SOTN)
Volume III would feature "HD" remasters of Circle of the Moon, Harmony of Dissonance, and Aria of Sorrow.
Volume IV would feature "HD" remasters of Dawn of Sorrow, Portrait of Ruin, and Order of Ecclasia.
As a huge Castlevania fan, I'd buy each and every one of those, even though I already own them all barring the DS Castlevanias. They don't have to do anything crazy with the visuals, just scale them to the Vita screen, and maybe clean up the NES games (perhaps remake those using some of the sprites from the PS1 and DS titles).
I'd pay even more money for a deluxe version, that features all 4 volumes, if they don't want to do multiple releases. I just want more CV on the Vita! I've been playing Symphony of the night for damn near 15 years, and if I can't get a new Igavania on the Vita, I'll settle for the old ones, and the classic ones!
*cries in a corner*