I think the beauty of this MOD is it's simplicity. A player is doing a poor job of managing unhappiness and therefore population emigrates to other civs or city-states who are doing a better job of managing their unhappiness. Makes sense.
IMO, Quiet Man is over complicating things. Mannu's suggestion of a worker spawning wouldn't be overpowered, but I think that a settler spawning would be overpowered.
IMO, the complexity of this MOD should lie in dealing with the rationality of how severe the penalties should be, how often a player should be penalized, what factors should contribute to being penalized, and who benefits. Along those lines, I like the way the rules are being developed and implemented so far.
As a suggestion though, I think that: within a civ that has become so unhappy, for such an amount of time as a citizen or citizens wish to resettle, the cities that have NOT invested in infrastructure devoted to happiness should be the first in line to lose population.
For example, a city that has built a circus and coliseum should be much less likely to lose its population than a city that has built no such infrastructure.
Also, I think that the size of a city should matter in this equation. In other words, a large city (in relation to other cities in the civ) with no infrastructure should be much more likely to lose population than a small city with no infrastructure.
Also, I think that when population chooses to resettle, they should be most likely to resettle in cities or city-states closest to the city from which they move from.
In other words, when a population chooses to resettle, I think they should resettle in the closest city that will make them happy, i.e. a city with infrastructure AND in a civ that can take on the added population and still remain globally happy.
I would further suggest, along the lines of revolution mod, that the player receive a warning when and where population is about to flee from. The player should then have a chance (3 turns) to keep the population by bribing them or by meeting their demands. This would require a system of reminders or some other visual cue. Revolutions mod had a good system as I remember.
Bribing the population would keep them settled for 5, 10, or 15 turns depending on the size of the bribe (50, 100, 150 gold respectively, but increasing at each era). After which, if conditions in the civ haven't improved sufficient to their liking, then the population would flee .
On the other hand, the population of X may accept a building built in city X to keep them settled. For example, the population might demand a circus in that particular city....the player would then have a fairly short amount of time (10 turns) to fully appease the population by building the building in their city. This could prove difficult because it may take more than 10 turns to get the building built. Thus the player may have to work to raise gold to purchase the project, or the player may need to bribe the population long enough to get the building built.
These suggestions would help add one of the key domestic element missing from C5, local politics! Here, the attitudes of local populace forces a player to pay prompt attention to not only global happiness, but also forces the player to not be negligent in dealing with the needs of local populations. I like the idea of C4/C5 hybrid when it comes to local v. global population!