Or he could go for the Rondo/CV3 kind of layout - Stage by stage, but you can choose different routes through the game. I do however think that the game would have to be longer than the old school Castlevanias, and definitely have more routes than the games I mentioned. Also; save feature/level select (after you've beaten a certain level). It would probably make the game a bit easier, but also more up to date with what gamers of today expect.
Oh, and the graphic style from the previous three DS games has got to go already. Ecclesia had new sprites alright, but the game looked pretty much the same as PoR and DoS - oddly cartoonish, especially when compared to something like Super CV4 (Which, by the way, is what I think Konami should be aiming for, visually)