Ok, so you want to abuse exploits so much that you would rather not even discussing, so others don't know about them and therefore won't be fixed. This is very surprising. Sure, in single player you can do whatever you want, including cheating, but I would prefer if all bugs and exploits (or as many as possible) to be fixed.
Why is exploiting the game so much fun? I always thought that the fun thing is to develop your empire and make decisions that makes sense both for strategy and immersion. Exploiting the game is (like we all know) very gamey, gives an unfair advantage and ruins the immersion. You don't do a thing, because it makes sense. You do it, because of details of the game system.
Doesn't it feel more wrong to be punished, because you have a resource? That's the case right now.
I don't see this as an exploit or a bug. It's using the rules of the game. I'm not breaking the rules. You play the game you like. I enjoy finding mechanics that build an engine that produce results. You apparently enjoy other things. Good for you.
Someone asked why you would refuse a gift and I explained a couple of reason why you would do that. I'm not holding anything back. Not keeping any secrets. That said this discussion that some, including you, keep bringing up each and every such time about how this is an exploit and all things should be fixed is starting to get a bit boring. There is never going to be a perfect system. There will always be rules and limitations and as long as there are there are ways to "exploit" or game them. This is not something I would put high up on the list of things to fix. I am not even certain that it's actually broken. Yes it is gamey but it's a game we are playing. Not a simulation of reality.
As I said I don't think this is an exploit. It's me making a choice -- accept gift now or hope that it will be a better outcome for a better reward a bit later if I wait. Each choice have a consequence and a cost involved. How is this an exploit? I'm using the rules as setup by the game. A lot of things in that regard are a bit gamey, every decision I make in the game that the AI can't due to all it's limitations is gamey. If you want it all to be equal I guess all you can do is watch AI play vs AI and just observe it.
If you want to translate it to reality, for some reason, you could say that by selling all my resources I'm creating a short in my local market in hope of future gains. I make more from selling things to others then making them available to myself. Eventually a need or want will rise local and I'll be rewarded for solving that problem then. But it's a gamble. It could fail. There is risk involved, even tho low. As it stands now then we, AI and players, having large stockpiles of resources nobody wants one is left to ask why would you even have large stockpiles of things nobody wants. The monopoly bonus then makes no sense what so ever. Nobody pays for things nobody wants. A monopoly on something nobody wants isn't really much of a monopoly. So why would you gather them up? Why have multiple resources accumulated if nobody wants them. It's a basic part of the game, accumulate resources and sell them to others that want them. If they don't want them, make them want it.
Also isn't that how things work tho? Things you already have don't really count. You have them already. You are gaining the benefit of having it already. You always want to experience things that you don't have? You rarely get rewarded for things that you already have or have done. You get rewarded for doing, trying and getting new things. For doing things. Not for just being. If you don't like the city-state quests you can just ignore them, once in a while some of them will complete just by accident anyway.
So you are not being punished for having something. You are reaping the reward already for or of having it. People get happier etc. So what you want is basically double dipping for nothing then. You want to be rewarded for things you already have, things you have already done. Rewards for nothing. And this is somehow not gamey?
That said I foresee that there will be issues and problems with the city-state quests if we start to hand out quest rewards for things we have already done in game to. It will also probably be a bit spammy and weird to note that quests just complete for things already done. So is this going to be limited to the resource and luxury quests or will it apply to other quests to? Cities already conquered, population already converted to your faith, roads already built, wars already fought, denunciations already made etc. What makes the luxuries and resources in that regard unique or more worthy then the other things?