I hope you're completely redoing the layouts too instead of just adding on because Simon's Quest's level design was simply abysmal.
The Parts of the Stage are gonna remain, but yes, the overall structure will be completely different, same goes for all the other "mansions"
Keep some of it, though. Or else you're loosing the nostalgia factor and might as well be making a brand new game insead of a remake.
The nostalgia factor will be where its remebered the most, Outdoors.
Iintend only to add on to the outdoors parts, but for the "Mansions" I have to make them completely different from the outdoors to contrast each other, to transition the mood. I will not change the big Picture of Castlevania 2, but I will add all the little details that the original lacked.
Generally when I design a stage that is supposed to represent a building I like for it to have elements that make sense to a real world building of the same type and not just have the 'game' stuff only.
For example, in a large mansion one would expect to find guest rooms, servants quarters, a large den, a small library, that sort of thing.
I estimated that this mansion alone will be 1/4 - 1/2 the size of SoTN's castle, all all the real world elements will have to go in or else things will get boring.