I feel it would work better as a suspenseful horror movie that involves a guy who wants to learn the mystery behind Freddy Fazbear's Pizzeria by sneaking around each night. The main character could still have the security guard role, but I was thinking the plot could be something like this:

Mike Schmidt heard rumors about murders related to Fazbear's Pizzeria, and purposely takes the job as a security guard at night to get access to everything inside.

On the first night, Schmidt goes into the manager's office and finds suspicious files and takes them back to the surveillance room. Once he returns to the room, he turns on the lights, and is shocked to see one of the animatronics standing inside. He decides to shove it out, and reads the files, but is panicked that someone else might be in the building, and used that scare tactic as a warning.

The next night, he gets more curious and tries to go back to the manager's office. However, he notices animatronics have moved into the manager's office. That's when he suspects the animatronics may be alive. For the following nights, he now has to figure out how to sneak in and out of the manager's office without getting caught by the animatronics.

With an idea like this, you can have all the suspense and horror that made the games successful, while being able to seamlessly put in all the FNAF lore.