Terraforming in general may be too much *if* the AI utilizes it. In some of my older games I'd terraform to the max and my planets were often in the class 40-50 range. On an insane map, and assuming everyone does it, thats going to be a LOT of resources to go around. The last 2 projects i believe, especially, generate a tonne of extra tiles.
Hence the reduction to 1 of each level per colony. I'd actually rather they allowed terraforming improvements to set a maximum planet class rather than piddling about with land %, then I could cap them all at 25 or so, but that's not how the XML works.
Star Names - I know you mentioned you fiddled with it quite a few patches, but how about contacting the star names mod guy, and incorporating his? The star names in the base game are pretty ridiculous.
Low priority, but eventually I intend to add thousands. Hell, if people post cool ones in this thread I'll add them.
Starbases - I know you mentioned you were going to take a pass at them at some point, but they are getting further out of whack as time goes on. Now that you can stack defenses on ships much better, the defensive modules are all but useless. In my current game I'm still a few techs from the end, but a tiny fighter has more defense (and in some cases offense, but its not in all categories) as a fully upgraded starbase. I know you hesitated before, but why not allow starbases to be formidable defensibly *if* we decide to pour constructors into them. There are a lot of defensive / offensive upgrades to chew through, and even with most of them in place they are still pretty god awful in combat. This is especially noticeable in the mid game, but their offense do get OK in the late game, even if their defenses are still pitiful. Those extra hitpoints are challenging in the early game, but by the mid / late game it's often just good for a couple of seconds before its destroyed.
They had a pretty healthy buff not long ago. And tbh, I don't want star bases to become too powerful' they're civ forts, not death stars. I'm only really concerned with how they do against 1 or 2 equiv-tech enemies, more than that and they should be in trouble.
Drengin Tech - under the AI these powers perform very poorly. I guess their schtick is supposed to be that they are good at ground combat? Since the game doesn't really utilize this at the moment (AI rarely invades even if it has an overwhelming advantage) might they need a buff in other areas? They seem to do very poorly in all my games.Malevolent ideology may also play a part in this, as it does seem to play out as the weakest of the 3, but I think there is plenty of room for improvement in the Drengin tech tree alone.
I've seen the AI wearing enemies down quite effectively through ground combat, actually; it works kind of like I want it to, with multiple invasions required to take a planet and extremely bloody campaigns. I juust wish they'd recognize that sending 2 or 3 transports might be a good idea.
As to Drengin tech being underpowered... depends very much on the race using it, tbh. There's some races which do very well with it. But I'll be looking through the techs more closely and doing some serious rebalancing at some stage; I've been generating some useful excel spreadsheets and suchlike with Powershell over the past few weeks while I'm waiting for SD to get 1.4 out the door, so I have lots of data to work with now.
3 way choices/specializations - Going by whats in game, there is almost always a BEST choice, a clear (but distant) number two, and a pretty dismal number 3. There are a few that are fairly balanced but seem few and far between. This could be a text update issue though?
As above. The big problem with these has been that, up til recently, more or less everything was so out of balance already that there was no point making adjustments.
Planetary strategic resources - I pretty much ignore these for now, as a 1% bonus just isn't worth it for most of them, and the fact that you can only trade for 30 turns, make it not worth the effort. It's not like i'm flooded with them, even when my empire is 50-100 planets. It could be interesting if they had more impact.
They stack. As such, no, there will be no buffs here.
Hyperion Buildings and the AI - They don't build them. I'm not sure if its possible to make them, if not, the AI bonuses should reflect the lack of them (ie more hull space for even Normal AI's).
I can make them build them. Low priority right now, though.
Filler components - More of a question, really. So glad that you caught the engine fillers, but I don't know too much about how fillers work, can you have multiple fillers? Since the blueprints end up with quite a bit of extra space to 'fill' I'm hoping the AI doesn't end up with just a massive amount of just one extra type of component (wether it be best defense, or offense etc).
It runs down the list and then repeats.
Cargo / Colony / Troop transports - These go pretty fast in the late game. I can abide the Cargo / Colony ships going fast I guess, but the Troop transports can get up into 30-40 moves territory. I'm guessing this might be an issue with the galactic speed limit, as cargo ships are starting tech, and you wanted them to not move so slowly in the beginning. I'm not sure if there is a creative fix for this, as generally speaking, cargo ships (other than possibly trade ships) should not be the fastest ships in the galaxy. If there is a creative solution that preserves their early game speed, without making them uber fast late game, I'd be all for it. In the mean time possibly increasing the troop transports mass might make for less engines (and less super fast troop transports). Just don't do anything to change the ability to get two constructor modules onto a cargo ship or I will cry. Constructor spam breaks my soul

Yes, you more or less hit the nail on the head, it's quite hard to balance them properly - especially when, if I nerf cargo speed we not only have more pain with constructors and a slower early game, but players will just switch to making them with medium or large hulls.
Nebula - I saw you are going to make these bigger - GREAT! Can you consider making some of them impassable? That could spice up the map. Also, I know you edited the effects of some of the nebula already, but I can't make use of them tactically because the descriptions are still leftover from the base game. Plenty of them still say they reduce moves by 50% but many no longer seem to do that in game.
I don't think we can do impassable. More effects would be cool though. The nebula changes are just one of the things I'm hoping to do to the map; I'm hoping it's possible to do something akin to gravity wells as well, increase the size of star systems, see if it's possible to add more nebula types and just generally make the field of play a bit more exciting.