I definitely like the first idea. Having a profit or "one who hears god" is a cool idea. There could be a new building that they are tied to or the preexisting god-email site could get upgrades. Early game they could be shamans and such and the role could evolve as the Nuggets evolve, influenced by how each player plays god.
You second idea is interesting. I think it could fit in well with the archive or the holy-site/god-email site. I think the holy books should be written by Nuggets, as their society grows and researches new things. So maybe not direct "laws" from god... but the Nuggets' interpretation of what god wants according to what research is done and how the player uses their "god powers", etc.
The concept of "missionaries" is interesting. The idea that they might be able to "bring home" exile Nuggets is cool. Sort of a non-violent way of dealing with it, rather than wiping out the exile camps. I was thinking rather than assigning the role of missionary to one or two Nuggets, perhaps certain laborer Nuggets can be gifted with "divine light" or something. A new god-power that lasts for X amount of time and makes those gifted Nuggets want to find exiles and "save" them from exile.