I think you have the foundation for a really cool take on FNaF, but the only difficulty I encountered was when I'd leave the office to reset the vents. Having the animatronics wander down the hallways every now and again seems like an easy way to increase the challenge a bit. I'd also add in some sort of acknowledgment that the player completed the five nights, as well as the good old nights 6 and 7 with a bonus ending of some sort. Something as simple as a newspaper article or picture of your check/pink slip would be cool. Anyway, keep up the good work!
Here's my no-commentary playthrough: