It seems that there is something of a hole in the diplomacy with City States. Further, the labels really fail to properly reflect the mechanism being labeled.
Just what does "Pledge to protect" really mean? What _should_ it mean? I read "Pledge to protect" and get the impression that the idea is that if the CS is threatened -- bullied, extorted, invaded, assailed by barbarians, etc. -- the pledge-giver is obligated to to dispatch at least _some_ military force to bolster the CS garrison. X turns later, barbs dead, bully backed off, invader sent packing, the pledge has been upheld. Failure to send those units constitutes a breach of promise -- and how _should_ your Reputation be impacted once it is commonly known that you don't keep your promises? -30 across the board with EVERY CS seems appropriate, I think.
Gift-giving: How does one _know_ just how much is enough when giving? Obviously, the bigger the bri-, uh, gift, the more likely to get a favorable and larger reaction. But I'd think it was more reasonable if the outcome was random, modified by a variety of factors. _Probably_ +30, but with a +/- of up to 20 (?). That seems more logical tto me.
Alliance -- Obviously, a Military _alliance_. Mutual Defense Pact, Lend Lease, Foreign Aid, etc. It's a _commitment_. So if anyone declares war on the CS, the player should be obligated to declare war on the aggressor. Failure to fulfill that obligation is an even bigger breach of promise than failure to uphold a Pledge to Protect. So, CS Influence across the board = -50.
What's missing but has been present in the form of Alliance as it _is_ already is a Diplomatic Accord: We help you out by doing you favors and Foreign Aid, and the CS reciprocates by returning resources and less tangible things like Faith, Culture, Happiness, etc.
Resource improvement investment: This doesn't feel quite right as it currently is. You send the CS the necessary cash to develop a resource and then IF YOU'RE _THE_ ALLY of the moment -- you get those resources. But in practice, what is being modeled is Third World Foreign Investments. The country gets an new/expanded industry which = more, and better-paying jobs for its citizens, while the foreign investor gets the resources being exploited. Win-(theoretical) win. Unless there is a MAJOR change in the politics of the CS, whoever paid for those resources should continue to get those resources, until such time as the CS becomes downright _hostile_ towards the original investor. (Then the industry gets "nationalized".)
Retract Pledge: There are the occasional Good reasons for taking back the pledge. Like when it's obvious to everyone that the pledge-giver is no longer in a condition that is good enough to back such a pledge. Yes, it's better to acknowledge the ability to fulfill the pledge is no longer there, but the recipient _still_ won't be feeling all that positive towards the pledge-giver for backing out of the deal. Better than finding out help won't be coming when they NEED that help. Others may not feel quite so peeved just because Civ A reneged on a deal with CS B. So, I figure the CS in question would be about Influence -20 while all the other CSs would be about Influence -10.