I'm taking some liberties here and there since it's not a 1:1 remake, and the falling bridge adds some "spice" to the first section.
Yes, it would be possible to make a Castlevania II remake since you can add hub maps, npcs, dialogues and shops (The engine also supports Heretic, Hexen and Strife, so all these features are native with no coding required).
I probably will not make it after i'm done with this (maybe next year?), but if i'd do it i'd take way more liberties to improve the original, with good puzzles, good npc dialogue, more enemies, new locations, changes to the story.
The only hard thing would be doing the day-night system but i'm pretty sure it can be done since i've seen other people do it in their mods.