Abegweit
Anarchist trader
Well, I think with fine-tuning the unhappiness from number of cities and happiness from social policies (I also wanted to add happiness from the number of technologies that you have researched, but it doesn't seem to be possible with XML editing), you can have "a glorious empire spanning the globe" in the late game.
If you want it in early game but eliminate ICS, I don't see a reasonable way to do it. Maybe positive happiness from population?
Edit: I have another idea: happiness buildings should have a minimum city size (doesn't seem to be possible with the current XML tags either).
It seems to me that the best way is not to beat ICS over the head but to make bigger cities a more attractive alternative. Larger cities are more efficient than smaller ones. For example, far fewer buildings are required per citizen (like one library for 20 citizens instead of five).
Start by fixing the abominable growth rule to make it more or less linear like every previous version of civ which would allow cities to grow to size 30 or 40 like they should when your "BFC" has so many more tiles. Then add more interesting buildings that only larger cities could possibly support, including a proper civ 1-4 style granary and more stuff for happiness. Dual-benefit buildings like you had in CIV4 (forge, market, etc) make for more interesting choices and add value to big cities.
ICS works because it is efficiently generates gold and beakers, which this game revolves around. Bring back food and hammers to make larger cities more valuable. What were they thinking of when they nerfed mines and farms anyway?