I described how to change this setting a few posts ago:
Link
Ah thanks, I missed that one
I really can't see any upside to the current CS setup though, and I can identify a lot of negatives:
1) Trade becomes much harder. On the current Terra map setup, I usually spawn quite a ways away from my closest neighbor. City-States usually bridged that gap and allowed you to trade with someone until the major Civ empires got close enough.
2) It weakens the CS civs (Greece/Mongolia/Sweeden). In my game there was only 1 city-state anywhere near me that I could find, and one I found later on the other side of the Ai Civs. If I was playing any of the CS focused civs I would feel completely screwed out of my UA until Astronomy.
3) Many Civs will have 0 CS allies. This just feels odd to me. City-States are one of the coolest parts of the game, and to basically relegate them to only the 2nd half of the time playing doesn't sit well with me at all.
4) The map felt too easy to expand into. While exploring I found something like 6 spots I wanted to settle on and was easily able to grab them with room to spare for my neighbors. Now I don't want it to be super-tight "OMG I can't even found a 3rd city!" situation, but after founding the 6 spots I still had 3-4 open spots I could have grabbed, and this is by Astronomy! I had no reason to fight anybody for anything
The map is just too big! Putting a few CS back onto the "largest continent" would make things tighter and encourage fighting for territory more.
5) I really enjoy the City-State Diplomacy mod, and this setup relegates it's effects pretty much until Astronomy and later. The whole point of the mod is to make Geography matter more (City-States nearby are easier to control), and putting a total of 1 city-state next to you means you have no choices. You don't get to think "hmm, do I want that culture city-state to be my ally, or do I go a bit further to get that military CS?" You only have one choice, and that's if the AI let's you have it.
Needless to say, I'll be utilizing your tweak to change it to 50/50 I think