So the NPC can just be something like a pet that can be in plugins like !store, but there is probably better stuff on gamebanana.
And spawning would work something like this:
https://www.youtube.com/watch?v=OqLZRtwmiVI
Go to 50 seconds. You just have a menu and you can spawn the NPC that you need.
And then depending which NPC it is, if you interact with it (maybe press E) or just come in its radius which can be marked with green circle lets say, it does what its programmed to do.
So for example, there can be NPC that just opens up a certain menu for you. Simply a command gets run when you enter a green circle, like !store. Plays a simple sound aswell after its done.
Or some other NPC can give you a random weapon.
This is a really good idea as it allows you to customize each map so its not the same like other servers and i really think its not that difficult to make.
I can pay for this.