Actually this idea is more about recruitement. In general a good way of recruiting RPers is to run into them or better said let them run into you.
So roleplaying in more alive areas is a good way to stumble upon new players for the guild - and as debated yesterday we want more.
So the godfather idea actually is quite good here as the godfather could send his apprentice literally every where speaking with any character (godfather also being the NPC if needed) So targeting taverns, mage or warrior guilds in bigger towns or frequently visited outposts would be a good idea go gain members while RPing.
Also RP in bigger towns themselves are a good way to get known. I myself joined 3 RP guilds and i ran into all of them by accident while questing or in a tavern.
So plots focusing on politics / diplomacy or getting knowledge from say mages or travellers could really be a good way of recruiting while playing.