0.6.3 adds dead bodies, right?
What about LIVE bodies!?

Researcher/Janitor/Electric/etc. -Run from you and will report about to MTF/Guard (D-class in past is criminals, right?)
Doctor X-SuperResearcher with name on this badge. I don't know, what they will do when saw you (Too runs away?). They can have something intresting!
Guards-Same with MTF, but less annoying (AKA Not very high spawn rate) and don't gonna complete the objectives.
D-class-Helpers Or Robbery!
Chaos Insurgency?
OverWarden-Will shoot you on sight and run away if out of ammo.

Not a good idea, as everyone inside the facility were evacuated, also, the game wont support so many AIs

Everyone else was evacuated or killed when the breach happened, so finding anyone alive would not be easy.

They could be made into small cut-scenes though, like a rare chance of a guard appearing once in a seed and when he turns towards you, 173 appears behind him, dropping down from the ceiling, and the guard will tell you not to blink or 173 will kill him.
But you have to blink and 173 kills him, and you then have to run away from 173 or you will be killed of course.

Same could happen to a scientist but it would 106 coming up through the floor and pull the scientist with him through the floor into the pocket dimension, or 106 walking out of the wall and grabbing the scientist and pulling him through the other wall. The scientist would need some lines of course, like yelling "help me!" or "get him off me!". Next time you then enter the PD during that save file there could be a blackened body in the main room with the 8 hallways, covered in mucus and rotten some places, with his lab coat being torn or rotten apart by the effect of 106's mucus.

Building a bit on your idea, if you don't mind me doing so.

I support this idea fully. It'd be a bit weird though to run into a Scientist and then the MTF come and kill you, but.. that'd work out.

Most scientists/staff personnel (95%) did get away into an evacuation room/shelter. I'm positive many Class-D's didn't make it, but were killed by Keters/Euclids during testing. I was thinking that there could be dynamic AI in the distance, actual guard NPC's in those containment rooms fighting those Keters/Euclids and dieng, or perhaps trying to run away and hide, then every playthrough would be different and unique.

There could be some cut scenes like in The Suffering, where you get to witness the horrible deaths of those around you.

I think some of the aforementioned ideas where maybe a scientist screams out help before being dragged away could work, maybe he's being chased by 096 and warns you not to look before he gets a hug off 096

This could be certainly interesting. Once the doctor models have been prepared for the intro, I could see the possibilities of seeing one run down a far hallway in the distance, only to be found dead moments later.

I think other people for scripted events could be nice, too. Seeing a D-Class trapped in the small control room with the glass panes, or several guards being attacked by 682 outside a blast shelter.

Blah... I saw Regails's points wright...
"They evacuated faster with secrets passages, what player don't know..."
So, i request to lock this thread and continue suggestion about "Room Stories".