NPC (Stealth) Behavior + Prone

Prone request:
Enter command in console that TOGGLES prone. For example enter “prone” in console and you will go prone, as in lying on your stomach, like in MW2.

My request is for a lua script that allows players and NPCs to be stealthy.
So ex. NPCs sight could be lessened so they can’t see you from a distance allowing players to be far away, but in front of NPCs (indirectly.) NPCs cannot see players if they are crouching behind a prop (ex. a crate, or something that would require you to be crouching in order for people not to see you.) And I think this is already in the Source Engine, but if it isn’t, players may sneak up on NPCs by crouching or walking towards them because of sound. Perhaps being prone while in a field of grass makes NPCs not find you. (Probably impossible because lua can’t interact with maps?)

Now for NPCs. If possible. If a player does not notice an npc, the npc will sneak up behind them and melee them. Or NPCs will try to hide behind props, and shift to another position behind another prop whenever a player turns around. And NPCs will run away from players (like they do now) and hide behind world or props. And if they’re hiding they will try to sneak up on you and melee you, or they will surprise attack shoot you.

Now this probably won’t be carried out, I’m just hoping it will. Or if some of it IS possible, then try to do the possible parts, and ignore the impossible parts.