This is pretty neat, but it feels too easy. I do like how quickly the guards and the player move, though. It's unexpected for a stealth game, but it adds to the tension a fair amount. You've already mentioned the idea to add static lights, and I think that really would have helped the difficulty a lot.
Additionally, in the darkness of the levels there's a small readability issue. Important fixtures such as doors, keycards, and objectives can be somewhat hard to spot/differentiate from the rest of the level. It might've been useful to give them some small glow or something to help them stand out.