As for the surface, it'd actually be pretty cool to go there at night. More monsters & Cursed Bokoblins won't be a problem as we could receive the Loftwing headlight in the later parts of the game. An optional Lantern as a pouch item would be a good idea as well, not to mention a larger variety of nocturnal insects.
Oh, and Eldin's lava at night would be beautiful. I think the only bad thing about the surface at night would be the complete lack of background music. But that's part of the night's atmosphere and constrast to day.
The more I think about this the more I realise this is a decent idea.