Yeah, I was mainly concerned if a custom NPC could even interact with the rumor system. I had no idea if it was relationship based or routine based and have to script it in as a routine. Turns out, a few hours after I post that, I happened on the answer. It looks like only NPCs who are Friends or higher gossip with other NPCs can/will gossip with each other. So, yeah, I don't have to worry about making a routine for it. But thanks for the comprehensive amount of info.
I also found out while playing with the routines that after playing a session with dynamic mode on, it gives you the lua script from last session. So, I took it and spent last night learning some basic Lua and hammered out a shabby first script and told an AI look at it and tear into my mistakes while calling me a moron, while I fixed it manually. I'm going to test it out today and hope I don't get any errors.