7 & 8 sound very interesting. I would love to try out those changes.
9) skirmish, rather than all out war. I have recently been experimenting with small scale conflicts. Declare war, hit a couple choice targets, bribe my way to peace. Rebuild, give gifts, repair rep, do it to a second enemy. This works best with #10 below. I will say, this is my biggest wish of all changes for the AI. The player has to use bribes to end a war and sometimes it's not possible at all. But if we could have a state of skirmish, or border conflict whole new areas of strategy open up. This one change allows the threat "remove your starbase from my sphere of influence or I will" to be a real, legitimate threat, without becoming "remove your starbase from my territory or you and I will fight to the death". It opens the door for an AI to come from behind by making small gains via skirmishes without provoking a stronger player into wiping them out. And it allows the player the same.
10) target empire strength. If my enemy's highest power score is from his fleet, but he has junk industry, kill the ships. It will take him a long time to recover. If he has both, ignore his fleets, they are expensive and replaceable, hit the world that built the most ships. If his strength is tech, hit the worlds that have many tiles but no shipyard or that build fewest ships. Don't just hit closest spot, Hi him where it hurts. For the player to use this on the AI we need to be carefully observant. The AI at higher levels could use knowledge of player planets to know where to target the attacks. This crosses into cheaty turf, so maybe an icon on the side of a planet showing its focus? If there's not one already, I can't tell what any of those are except the morale one.
11) early influence land grabs. Drop cultural bases where they will expand, and where they will cut off expansion. Typically one or two tiles inside the enemy leading edge is perfect for unclaimed space or on the edge for a contested border. I'll edit with screenshots. Claiming map edges on the backside of a rival rather than just fighting their leading edge is also brutally effective. The longer influence builds the stronger it is, so it is better to lay them down early and collect "interest" that try to brute force it later when they are entrenched.
Detailed tactics by proposed AI difficulty: I admit I don't know how to do weighting on this, but here is how I wage culture war during the expansion phase of the game with visuals.
Initial State: Imagine AI is red (Drengin) and player is purple (Yor) http://imgur.com/8iN3D2Q off screen drengin has one colony ship coming and there is a planet just south of the constructor out of view (you'll see it in the next image).
Weak Beginner: http://imgur.com/YAxjPcD By dropping a culture starbase right where the constructor is, the situation will stabilize thus. Player has control of the southern uncolonized planet influence lines will meet and stabilize in the middle until the planet is colonized where the yor will begin winning. If Drengin try to colonize the planet they are three tiles into yor influence and risk losing the planet to culture flip. This might be too weak even though it is stronger than what the AI does currently.
Strong Beginner/Easy: http://imgur.com/NdJ1B5f By placing the constructor instead between the duranium and dead world, two tiles into Yor influence this is how it stabilizes. Drengin has control of the uncolonized world but Yor colonizing would move the lines and there is low risk of culture flip. But if yor is too slow and Drengin takes it, the yor planet is slowly going to be pressured. North, however, all three separate yor spheres of influence will merge, making a solid firm block. This is a good move for the Drengin AI but not a great move, what I would recommend for beginner or easy.
Normal+: Remember in the initial state, where the survey ship was? What if the Drengin AI moves the constructor past the yor front lines. http://imgur.com/P2lMCIV Now look how this stabilizes. The player's southern sphere of influence is cut off. those red lines show tiles of player influence that were taken over on the action of placing the base. The north west player sphere is far from a planet, it will exert less pressure than the culture base, but the southern planet will push into the drengin starbase unless it is reinforced. Drengin AI influence will not only split the southern planet off, but also it will expand west into unclaimed territory, blocking the yor player from multiple stars as indicated by the colored arrows. In the middle, the purple line shows where the north east influence will meet, it's hard to predict who will push harder I'm guessing Yor player but not by much. What is important is the lip areas where red drengin influence barely extends past the purple yor. If it grows faster, even 1 tile faster, it will start to surround the yor. If the yor gets the first expansion there will be a tie and the diagonal line will extend off giving drengin a big swath of space. This is quite a strong attack.
Best Move: instead of dropping the base in between the two spheres of influence, take advantage of the weak north west and drop it three tiles into yor territory. http://imgur.com/yQA7DkN Now the yor player is pretty screwed unless he can get new sources of influence down into this conflict. The middle area looks almost identical, but look west and south. Thanks to a nearby planet the southern yor influence line is already at its maximum growth. A Drengin colony on that unclamed southern world might have enough influence to survive without culture flipping (but it a risk) and that would definitely overwhelm the yor player's southern world. In the north west, this placement has clamed more than double the tiles already and it is not extending in parallel diagonal lines, it is an expanding triangle that has cut off the yor from two of four western stars initially and the third is going to fall once the yor southern planet is flipped. With another contstructor closer to the north western most star the whole western flank of the yor sphere of influence can be rolled over and their core worlds squeezed from both sides. But the Drengin war fleet is on the Yor's eastern flank so the Yor need to defend on two flanks and two separate tactics both culture and military. With just one or two constructors the Yor player is surrounded and has lost access to a huge chunk of territory. If there are other players to the west the Yor cannot meat them without crossing Drengin lines cutting them off from trade opportunities.
Right now the AI basically just drops mining stations to claim resources, and those have static one-time influence gains. This kind of influence war tactic the AI currently has no defense against, and it is something a strong AI could use successfully against the player. Especially early in the game when influence totals are low and so the base culture station is at its most powerful and can claim huge tracts of land.
12) because of 11, the ai needs to stop colonizing deep inside hostile influence unless it wants to give world's to that other player. If colonizing the planet will not move the sphere of influence lines on the map, the AI should not colonize the world at any difficulty higher than beginner, and maybe not even there.
13) when trading the ai doesnt know how to add up credits. credits per turn have waaaaaaaay too big a value when I ask from the ai. I can get far more credits as a lump sum than I can as ongoing payment.one example was a recent game where the ai refused even 5 per turn in exchange for a free trade agreement, but happily gave me 800 lump sum and considered it extremely generous. I forget the duration of a free trade agreement, but it is not 140+ turns. Dunno if this counts as exploitable but it greatly hurts the ai when their income is high but bank is low. Edit: Latest patch appears to have removed trading for credits/turn so I am striking out this tactic.