NPC should talk to the NPC only when they're addressed. They can talk as much as they want between themselves (about mudcrabs and arrows in the knees...) as long as they don't spout generic nonsense when I come close to them.
I think that would be the best and simplest solution. They wouldn't have to record any more dialog or anything, and it can't be that complicated to do if one of the first mods to come out did something similar. But it Todds got the attitude of we don't give a stuff then I guess that's that.
I think the worst ones for me are my wife and housecarl. Whenever I'm home I leave the housecarl outside, and I'm almost at the point of sending Isolda back to Whitrun just to get some peace and quiet, which would be a shame. But she's bugged anyway. She said something about if there's not going to be a ceremony I want my ring back, so apparently she doesn't think we're even married.