This is my suggestion but feel free to type yours in the comments!

Note:Npcs arn't possible since it's a zombie game. Plus nelson probably didn't add NPCs that could harm you. Yet.

1. Keycards
I know what your thinking. But dude,keycard doors arn't a thing yet! So 1.Just add them in for decoration. People could use the point action with the keycard to look like they inserted it. and just make and add keycard slots! Oh,and signs so they know what levels can be used to open the door.
2.Divison Outfits
Here are a few...
Logistics Department
(Imports new tech and supplies. Uniforms are exactly like foundation personal or Security Department except have logistics logo.)
Site Technician
(fix problems like malfunctioning doors. Their uniform is a gray outfit with a tool belt,and the SCP logo on their shoulder areas and back.)
Bio Hazard Cleanup
(Clean up hazardous messes and waste given by certain SCPs ((Class-D's only clean 173s chamber.)) They wear a yellow hazmat suit and gas masks.)
Foundation Personal
(These are basic members. They wear a completely white outfit with a red tie and the logo around their heart.)
Mobile Task Force
(Carry out missions NON-breach related. Wear a SD uniform except the white is a dark blue. and SD helmets.)
Internal Security Department
(A Sort of-police. They take out traitors and keep the facility safe Infiltrate and Rouge Personal wise. They wear a completely dark uniform with vests and wear special gas mask helmets.)
Chaos Insurgency
(They are a group that steals and raids the foundation. Taking anything and leaving few survivors when they can. they wear a completely black uniform,a black helmet and a white and grey gas mask with multiple tubes sticking inside.)
Serpents Hand
(the serpents hand breachs the security of the facility,making it vurnerable. They wear black outfits with green vests and helmets,and black masks.)

Thats it so far,I will add more!