I've been trying to find a way to break ICS in my (currently personal) mod, but I'm just not seeing the type of things that would incentivize this. Some of the ideas that I can't seem to get to work: 1) Increase per-city unhappiness, but give +1 happiness to some early buildings (the granary sounds obvious, and maybe barracks or walls as well). However, I don't see how to increase the per-city unhappiness from 2 to 4. I'm also not sure what the AI would do with this; at high difficulties it's pretty much unconstrained by happiness anyhow so it doesn't matter that much. 2) Era-based happiness bonuses along with (1); with an extra +30 in the modern era you can get bigger/more cities, and it avoids weird happiness effects. This doesn't seem possible; the only things I can see the era can affect are policies and the cost of research agreements. 3) Have per-city unhappiness be non-linear (aka the real fix). I just assume this requires the DLL. Some ideas I haven't tried, but am considering: 4) Give cities a free building that has a per-city negative effect (i.e. -1 gold per city) as well as some bonus (population produces science points). You could sell the building, but then you lose ICS benefits. 5) There's a table Improvement_AdjacentCityYields - perhaps certain improvements won't work as well next to a city? It would encourage cities to be placed far apart, at least. 6) Limit settlers. There is InstanceCostMultiplier which might work, or maybe a limit of 1 active settler at a time?