A game based on the SCP Foundation. I would pay so much money to play that.
Oh yes, this. So much potential. There could be a Half-Life-ish shooter where you need to fight through escaped subjects, or perhaps it could be sort of a micromanagement game where you need to make sure the subjects are properly contained and conduct experiments.
First Person, Yes. Shooter, No.
I think it would be better with no HUD, interaction with all kinds of SCPs (including "safe" ones), realistic guns (as in powerful, ammo is very limited, reloads take awhile, and if you don't aim/be at point-blank range you won't hit anything), enemies who have be killed by an
other option, and the map should be random each time you play(which shouldn't be a problem as you will be underground).
You should be able to order around Class-D personnel, steal ID cards and such from O5s, log on to computers/find research logs in order to find out more about SCPs and how to deal with them.
Overall your main goal should be to contain the situation but, this doesn't necessarily mean killing all of the SCPs one by one. You could activate (or disarm) the on-site Nuke, call topside for reinforcements, force/trick them back into their containment areas, ect.