1: The ideology system still stinks and is WAY too dependent on colonization events. Ideology points should be tied into the influence system.
I'm amazed that after two major expansions the ideology system is still as primitive as it is. It really needs to be tied into an existing system like influence generating buildings in the same way that the CIV series social policies are tied into culture generation. I don't object to colonization events and other events as a means to augment your ideology points; but it shouldn't be the driving factor behind their creation. I think influence point generation should be the main way that you earn ideology points where influence gives you neutral ideology points that add onto the ones made by your choices in colonization events with the neutral points being able to be spent on any branch (benevolent, pragmatic, malevolent) of the ideology system.
2: More Planets should be locked behind colonizing tech in order to slow expansion.
I feel like colonization spamming is still an issue that screws with the pacing of the game. Has any consideration been given to expanding the concept of extreme worlds to slow expansion? Like initially all you could colonize would be planets that are a lot like your race's homeworld (Normal planets and breadbasket for carbon based, Aquatic planets for aquatic races, etc) and there are more tiers of colonization techs to unlock planets that at present can be colonized from the start (desert, thin atmosphere, etc). This would slow the need for colony spamming early on and make you feel less cheated by the AI beating you to a world you wanted.
3: Extending your ships range should be tied into building shipyards, starports, and starbase modules in order to slow expansion .
As it is I think that the limitations on ship range don't do enough to slow expansion. Colonizing a planet or building a starbase on its own should only expand your ships range slightly, whereas building a shipyard and a starport on planets or resupply modules on starbases would be necessary to significantly extend a ships range. This would likewise serve to slow the player and the AI's rate of expansion.
4: Give the player more control over generation of citizens by tying their generation into morale.
I like the citizens; but I feel that just throwing one at the player every 10 turns is a pretty arbitrary way to dole them out. I'd like to see their generation be tied into the morale system so that a high morale increases their generation while a low morale slows it. Likewise I'd like to see more ways for the player to increase their rate of generation by building improvements. I really like the buildings that let me train citizens later on in the game and I'd like to see that concept expanded. This would also make the morale system more significant. On a side note I'd like to see the morale boosting improvements on starbases make a return.
5: Espionage could use some work.
I'm not really thrilled with the way spies are deployed to planets. Disabling an enemy building seems like a weak way to spend a citizen and having to use spies to remove enemy spies from your buildings is an annoyance to the player. I'd prefer some sort of mission based system where I can send my spies to steal credits or tech, lower morale, or blow things up (buildings, ships, maybe even starbases) which takes time and has a variable risk of the spy being caught depending on the difficulty of the mission and the spy's skill; but doesn't expend the spy unless they get caught.
6: Minor Races (city states) should be expanded not removed.
I was disappointed to see minor races being pushed to the sidelines with the recent updates. I realize they weren't working very well in their current form; but I like the concept behind them and was hoping they'd be fixed and expanded not removed. For an example of what I had in mind, I'd point at Star Trek: Birth of the Federation a game that had a different system for interacting with minor races as opposed to major powers. This system allowed you to form trading relationships, alliances and even convince the minor race to join your empire (if you don't choose to conquer them) and if you could get them on board it would allow you to build special improvements that only that minor race could build. At the very least you could just give them all some rare resources to trade (nanites, techapods, etc.).
7: Improve Military Starbases.
As is I can rarely see a reason to build a military starbase instead of an economic, cultural or mining starbase. By default I think they should get a buff to their weapons defenses when they're first built. I also think their default area of effect should be larger than the other starbases since the buff they give to ships is their main purpose with tech unlocking further expansions to military starbase area of effect in addition to the expansions that effect all starbases.
8: More things for constructors to build aside from starbases.
Roads: Not actual roads obviously; but an improvement that lets you travel faster along a set path like hypergate lanes or what not. They can be built and destroyed at a set distance apart (10 tiles maybe) to greatly boost your ships rate of travel between them and would add an extra layer of strategy.
Minefields: You build them in a tile and when an enemy passes through they inflict a set amount of damage relative to tech level and they drastically slow down the number of tiles an enemy can move in a turn.
Sensor Buoys: I frequently find myself building ships just to station them to keep an eye on an area. It would be nice if I could just build an improvement to do the job for me at a cheaper cost.
9: More things to Survey unlocked by tech advances.
Like the archeology sites in CIV 5 basically hidden goody huts that don't appear until you've unlocked the tech that makes them appear. Maybe some of the dead planets could be scanned for research points or credits. Salvage anomalies appearing after a battle should be more common and I'd like the events where I find random derelict ships in anomalies or get flung somewhere by a wormhole to make a return.