Wishlist addition of mine that sort of relates to this... figure out a way to make the Terraforming spellbook not as cheese. I shouldn't be able to completely avoid an enemy chokepoint by just casting a spell on a mountain and making it disappear.
I would actually disagree with this. I find it odd that someone who supports political intrigue in the game also says that using magic to circumvent a choke point is cheesy. Right now, I think that the terraforming spellbook is quite nice as it gives spells to both raise and lower terrain, which gives one side the ability to tailor make choke points, while also give your opponents the ability to get around them. My only point for changing this spellbook would to add spells which went along with extra-city improvements. Like maybe, a terraforming spell could be made which caused a food resource to no longer give its resource for a few turns, or one that gave a few turn bonus to material production for old forests.
Here's a new one that hasn't been mentioned... Politics. I want to see some more useful political machinations available to us, and to the AI. The ability to attack a player under the guise of another ruler, the ability to deceive Ruler A into attacking Ruler B, or cause a general/heir to rebel against their King and either try to take the throne or break off and create their own kingdom. You could even create an alliance, attack your ally under the guise of THEIR ally (who now has a resource you want) just so you can attack them and gain that resource without breaking your original alliance. Or it could all backfire and now you've got 2 enemies. Maybe Diplomatic Capital could be a fluctuating resource, rather than just "political gold". And on the other side of the coin, the AI can do these things to you as well. You could get attacked by "Magnar" but really it was Capitar trying to incite a war between the two of you. This would require quite a bit of AI coding of course, so... you know, it's easy to just talk about it. Diplomacy Tech could really become a lot more fleshed out if you could unlock different political machinations, bonuses to "scheming" or whatnot in addition to the different options. I've yet to play a 4x game with a really fleshed out diplomatic angle, and I really think with a few right ideas, the complexity of this game could really expand, without overly complicating how we play it. It could create some interesting new strategies by getting others to do the dirty work for you.
I think there is a good point here about actions which have diplomatic effects, yet these suggestions would require a fairly large change to how player engage each other. Since interfaction combat requires a declaration of war, a unit cloaked in the garb of another faction could not simply attack without sparking a war. Honestly, I would hate it if an opponent of mine could simply start a war by merely building a unit and sending it on a suicide mission. That said, I think there is a huge amount of fertile ground for spy/stealth in Elemental. Maybe one could build a spy, send it to an enemy city to disrupt production, and blame it on another empire. This would allow players to deviously start wars or break up alliances, while also running the risk of their own plans being foiled.