Fix the default ship population.  At 2.5 the AI is tossing half it's raw production into space with it's 1st colony ship.  At base growth rates it will take the homeworld 25 turns to recover while the colony founded by the ship maxes it's raw production in 5 turns.  This must be terribly crippling to the AI's early game.

I don't like the old or the new population to production schemes.  I mod it to 0.92 and it feels right. (2 cents here)

Armor seems underpowered.  Armor components have the highest-per-tier mass requirements, provide equal levels of protection, yet counter the highest cumulative-damage-output weapon system.  I raised Armor Efficiency in my games to 0.3 to offset this.

Random anomaly defenders please.

50+ new anomaly outcomes please.  A fine DLC if it also adds a new type or two.

When, and if, the major game-shifting changes are passed, the improvements, ideology choices, techs, components, global defs, bassicly everything needs a global combing for consistency, utility, balance.

Consider bringing back the starbase moral improvements with the return of the 1:1 pop to production scheme.

Leave a gap between max and starting population on the homeworld so that potential growth is not wasted making an initial choice other than rush buying a starport and a colony ship.

Here you go:

Ground invasion demo

1. Perhaps it's just me, but I very often (read almost always) get the feeling that I am Team 1 and the AI, all of them, is Team 2 - regardless of AI personality and how strong, advanced, or extensive my empire is. That is fine for small deathmatch maps, but for bigger maps with more civs, this doesn't feel like an immersive galaxy.

2. It's been said above and in many other threads, but if there is a way to make colonization and starbase construction within another empire's influence only possible when at war, I would be happy.

3. Previous peaceful cooperation treaties (Non-Agression, Alliance, Research, etc) need to weigh as much as previous wars seem to when factoring AI diplomatic stances.

4. Have a look at the abundance settings for planets and how they interact with eachother. Can't put my finger on it, but something seems to be 'off' there. Abundant all setting has very often left me with the worst luck ever - one colonizable in intitial range, for example.

Yeah, once you start putting more than one abundant setting it seems to start taking away from everything else, personally I've never liked the abundant settings on the largest maps,  Large and below seem fine.

Music is already awesome

https://www.nexusmods.com/galacticcivilizations3/mods/36

Mechanics based narrative pressures:  Ideology as reason for alliance/conflict, Diplomacy affected by historic events and promises, more prominent display of these factors, especially involving an Espionage system, War Weariness, Inflation and other economic events with solutions based on UP interventions.  Anything that provides interaction between the various mechanics and their outcomes and effects on one another.  

More extensive Workshop support.  Where are mods and buildings and other workshop items?  I will mention failure to support custom factions in MP, not a pleasant thing that my customized faction cannot be shared in action with my friends and enemies.  That is a big thing of not meeting expectations of implementing your otherwise amazing customization.

A meaningful final game score.  It is a ridiculous ego boost factor, but it is something that should be obviously meaningful or removed completely.  Metaverse is presently nothing but a big data free disappointment, at least for me.  A replay the whole game feature, where I can start out with that lone first planet and watch all factions grow in an animated replay, with or without battle replays.

Custom defaults for dialogue box defaults, such as auto-upgrade on Planets, repeat last ship, repeat last planet improvement, etc.  It is a little thing that greatly affects overall micromanagement.

A control system for the free movement setting in the Battle Viewer where I can fly an invisible camera through a battle scene and make custom videos with cool viewpoints and transitions, even jump cuts like the automated viewer does,  and a little bit of automated programming to create new moves for the camera to use, even in automated battle view.  The battles are one of the most important events, at least visually, and should be fodder for lots of video posting acting as crowd source/word of mouth advertising of the game.  Where are my videos with a couple dozen ships on each side going at each other with slow motion emphasis on key ship deaths?  User manufactured eye candy, free for one and all.

Along with that, a sandbox where I can pre-stage battles with arbitrary ships and let them duke it out.  I think that would be a big DLC opportunity.  It is sort of like firing up the first campaign just to see those first big battles you set up.  Players should have the same set up and watch it go type interaction.  Again, home made advertising fodder.

Narrative interaction should be the goal of all mechanics and be considered in multi mechanic interactions.  Our history with other players should come up in discussions with other factions.  The present custom dialogue is difficult to adapt dialogue for, and this affects the ability to provide story type content.  I  have played with the concept with the present mechanics and it is very limiting.  It needs some open ended or logic/keyword based control.  It is such a great potential I would hate to see it not get some love and development.  Custom dialogue with custom behaviors would be a way to add value to workshop items as well, with narrative benefits and penalties possible.

I go for making them at all times. It just makes negative relationship points.

All of these are great ideas - I have an ask for a paid DLC myself.

An animations pack which would simply be a number of animated backgrounds and foregrounds for other races/minor races without any other information attached, they are simply animations that the community can combine and use (or not) for their own custom races rather than the majority of copy/paste races or static images for backgrounds and foregrounds we currently use.

I'd pay £10 easily for 30 (15 backgrounds, 15 foregrounds) for something like this.

Also, can we bring back diplomacy with minor races in Crusade please? I liked being able to trade with them before and broker distractions or bushfire wars between minors and other minors or even ganged up wars with Majors. Right now they are just "there" not doing much, I can't speak to them, I can't trade with them. I normally invade minor races early in the game for extra space because otherwise they are useless to me.

I can't think of anything else off the top of my head, but there have been a lot more awesome ideas already.

Here's my list. Mostly politics and government based.

1. Influence as a currency-influence generated by planets and structures are now used for diplomacy options such as tech trading and declaring war, etc. Civilizations can trade and conduct diplomacy with each other anytime instead of waiting X amount of turns. Players must now make the decision on what to use the influence points on. No more civilization A meeting B and C early game and immediately trading 25 techs between the three civilizations. Influence points can also be used to affect the United Planets. I usually skip influence structures in my games, this change would make influence structures more useful.

2. Bring back The Drath Legion-New ability allows them to use the influence to buy whatever other races can buy with credits.

3. Bring back the Korx race-They have new ability that prevents them from declaring war. Can ban civilizations from the black market and bazaar. The Korx are immune to bans with a new ability. Special ability to get a small percentage of credits of each black market transaction.

4. New Race for expansion-They can't use diplomacy and have no such thing as credits or money.

5. Black market: Civilizations can buy or trade resources from the black market. Number of resources available depends on how much other civilizations have sold. Can "Order" or "Fill Order"

6. Trading Companies. Can create trade routes within your own civilization with trade modules. If you're at war and playing on smaller maps with few civilizations, players are losing income by not being able to trade.

7. Pirate factions: Pirates should be divided into many different factions, depends on galaxy size. During mid game they should start attacking more civilizations. Pirate bases can spawn in asteroids or space maybe if territory is left in the FOW for a while. Bases can spawn legions of troops for invasion of player planets.

8. Ideology screen- Icons showing stats of the structures. Similar to icons on planet tiles with resources if players mouse over them. Allows players to see the stats of structures before hand.

Just to be clear:

2.6 as I write this isn't released.

You will only be able to build two cities on planets in 2.6.