Suggestion: NPC Manager system

By NPC i mean sims with specific roles that we can't apply to.

Can we please have a way to manage the NPCs our games create? Like a mechanic that allow us to choose which sims (existent or auto gen) will fulfill any NPC role like vendor, romanric guru, maid, mechanic, etc.? 

I feel like this mechanic would allow us to create the exact ambiency and stories we want with the sims we want, and that would be great for storytelling too. 

I say this because i feel like we don't need all those auto generated sims, specially if we have many EPs, and there are some sims i'd like to see in specific roles that are usually fulfilled by auto generated sims.

For example: Once i saw the Fyres couple as firefighters in Cooperdale High and i think it was so cool because Fyres... Firefighters... Other time i saw Marcus Flex as a detective fighting miss Robin Banks and realy liked it. I'd also like to see Don being here and there doing random gigs and many more.

I think i could even be more customizable so we can choose where they appear, when they appear and what they use, because i'd really like to create some ghost NPCs for Willow Creek and Granite Falls, and the Bigfoot NPC too.

EDIT:

I was looking for a way for it to work and i think it could just use the manage employees system we already have in the game where we can choose the sims and set their looks and actions (and the places they show up could also be added)