I have a mod focused on NPCs, but I didn't tried to import it to 1.4 yet, and no much ideas what the differences are, so... I'm also interested, how the codes might changed XD
I can help a bit as far as pre-1.4 concerned, but that's probably kinda outdated...
Regardless though, I'm curious about your NPC ideas, so, would you like to tell more about them? If you want, I might try helping with brainstorming too.