Mmm...yes.
I cannot even recall what flares used to be like in FF 1,5-2 years ago, or even if they were different than they are now, but it would add the immersion, the thrill and to the difficulty of nightly encounter if we had to rely on flares, flashlight, night or thermal vision. Especially in caves. Outside, the light of natural satellites (plural, even) could aid us, so we wouldn't have to use up aiding equipment or rely heavily on them. But, in pitch black caves, we'd only see as far as a flare would illuminate the dark. We'd hear the creatures moving around and some would blindly fire into the darkness, like, in the cinematic intro for FireFall. With night and thermal vision, this could be further improved.
Apart from moons, it would also be lovely to see more natural light-sources, in the form of bio-luminescent flora. Strange plants. Some campfires or torches hanging from fixture, the embers of which could be seen from far away, would also add to the look of the game.