At the base, the entire mechanic driving the CS for diplomatic victory is bribery, nothing else.
Agreed, but my point was that this is exactly the way you interact with civs for the most part in obtaining their favour - give them luxuries when they ask for them, declare war when they ask you to, making trades in their favour, opening trade routes that give them extra commerce, all fundamentally amount to bribery.
Civ V does a better job than previous Civ games at adding politics to interactions, with the importance of shared alliances/denunciations and now ideology, but at its heart the diplo victory has been a thinly-disguised "bribery victory" since it was introduced to the series (at least when it's not a "conquer everyone to obtain their votes/force them into vassalage" victory).
Influence with CSes basically works exactly like the modifier system in Civ IV with the exception that influence degrades rather than accumulates over time without any intervention by the player (and, of course, the exception that you now get to complete quests to earn that favour, something that was limited in Civ IV to occasional "a random event has hit another civ and it needs your help" events).
As for graphical crap, I'm not saying that the city states should have fully animated leader screen like major civs, thats not what I was getting at, and i'm not the type of person to want fancy graphics over functioning core mechanics.
Quite possibly not, but it does seem that you're letting the difference in graphics guide your perception of how different civ relations actually are. Pretty much none of the options you want for city-states are available to fully-fledged civs either, and the treaties that do exist - declarations of friendship - work "under the hood" in pretty much exactly the same way as CS influence: if a civ decides it likes you enough based on its positive modifiers, it will offer or accept a DoF. Relations with CSes are handled not very differently from relations with civs; if a CS decides it likes you enough, it will become your ally. Which boils down the essential differences between the two to the leader screens and the fact that the influence slider is visible for CSes but not for civs.
The only thing that particularly irritates me about the CS system is the inability of CSes to act in their own interests if attacked - a CS that has an ally has no ability to break the alliance to save itself if it's about to be captured. Also, in the World Congress/UN, "independent" city-states have no vote at all (if a vote comes up just as influence has deteriorated with its former ally, or if an ally has been destroyed, for instance).
The banning movement already effectively exists; walk through a CS's territory if it's not friendly and it will get angry. This is quite a good way of reflecting the fact that these are minor powers - they have no more actual ability to prevent a civ walking through their territory than, say, Nicaragua had to prevent US forces hunting drug-runners and terrorists in its territory.
And none of this is far from the way diplomacy works in reality - even the role of war (famously, diplomacy by other means) in securing a diplomatic victory.