Very much possible. It's just client side addons at the end of the day (in the form of addons and FrameXML for this). I have already ported the leveling system, loot system, char creation system, dungeon journal...
The water graphics are possible to replicate (Schlumpf has done it), however I am struggling as I have a missing shader or texture somewhere that causes a green tinge. Not given it much research.
Sunlight shafts etc can be recreated with better images that are overlayed.