Some thoughts on improving techs and new techs to add. Each of these below tech trees could be a mini expansion, and I would buy them all....
I like the idea of having a lot of smaller improvements to weapons as opposed to fewer large ones like in the distant suns mod.
What about adding an intelligence tech tree...might be fun?...you could do all sorts of stuff with spying, espionage, spec ops, etc. You could have cloaked ships in here, cloaking fields, sensors that allow you to see through cloaks, mis information or propaganda ships, which have special capabilities...you could do a whole expansion just on this...
You could have a ship that when it jumps between phase lanes, it transmits a signal that makes it look like its really a much larger fleet than it is so you could send 1 ship to another planet or a group of planets and the other people when they see it on the phase lanes could think its much larger than it really is and divert some of their ships to defend just in case. You could have a ship that projects itself into multiple places at once, making it look like their is 5 of them or something. The Advents illuminator ability could be moved to the intelligence tree for this purpose just like certain defensive techs were moved to the defense tech tree. You could research the ability to build deceptive defenses that don't really do anything, such as cheap missile batteries/platforms that appear to be real, however, when in fact they do nothing but are only there to provide the illusion of defenses. They would still cost money to build, however, they would be a lot cheaper.
You could have spec ops ships which look like trade ships of your opponents but are controlled by you, so you could move them around to insert teams behind enemy lines to do subversive stuff...
A new building could be an intelligence directorate or espionage center or something that would allow you to build these ships or would enable you to build them or to research other espionage techs....this is also where you would research counter measures to enemy deception, espionage, and spec ops.
You could also have an electronic warfare tree. You could have an electronic warefare ship that could jam enemy missiles, reducing their chance to hit considerably within it's constant area of affect. Advent could have a mobile propaganda ship that can produce culture from anywhere, but it should have to stop to deploy and it should be very vulnerable at this point and be unable to move while it's transmitting, and would have to undeploy to move again. Undeploying could be very slow. This would make for some very interesting strategies indeed. The ship should be expensive too. Vassari could have a comm jammer which would jam enemy communications with HQ for a limited amount of time reducing the fleets overall effectiveness and also preventing human players from giving their ships orders for a short period of time preventing micro managing. Each race could have a ship that does something along these lines, I am just throwing out an idea. While certain ships would have ECM type devices to jam things such as missiles and targeting systems, there should also be ECCM techs in this tree. This is also where you could upgrade your targeting systems to make your chance to hit higher or increase the number of targets a ship can fire on at once.
Perhaps the weapons and ship tech trees could be separated...one would be where you research your weapons upgrades and the other one would be where you research our ship prototypes.
For the ship prototypes, you could also make it so that certain ship prototypes couldn't be researched until the applicable weapon system had been, essentially making it so that you had to do at least 2 levels of research to get a ship...missiles and then the ship itself. There could be specific upgrades to the ships you could research though at the higher levels that would be really cool, such as increased targeting banks so the ships can fire more ships at once. Each ship could have multiple upgrades to it. Each ship could have it's speed increased, the number of targets it could target at once, etc. Strike craft upgrades could also be bought in here. There could be heavy strike craft, cloaked fighters, planetary bombers, etc, that could be researched. Also, carriers could have the ability to increase the number of squads they carry. With each ship upgrade, there could be a corresponding change to the look of the ship. The extra gun batteries would become visible, the extra hanger bays are shown.
Also, certain types of upgrades that could be researched perhaps could be very specialized upgrades to the ships that actually require you to purchase it and upgrade every ship individually. Say if you wanted to add additional Flack batteries to a capital ship making it much more resistant to bombers. If you had a lot of these, it could create some very diverse strategic choices. The total number of upgrades to a capital ship could be limited. Say for the carrier capital ship for the advent. You could research extra hanger bays allowing it to carry 2 additional squads, increased flak batteries, additional beam cannons, adding an additional number of beam additional beam cannons, or repair facilities (allowing it to heal nearby ships with its antimatter), or wide are ECM jammers which could reduce the chance to hit of all missiles to ships within it's radius. If you have a lot of strategic choices, but limited the number you could install, it would be interesting. Say you could only upgrade each capital ship with two of these upgrades....This type of thing could also fall under special weapons or secret weapons if you wanted to make a secret weapons tech tree, which if you did, the super weapons should be moved into here.
As for upgrades to the weapons, I think all weapons should be able to increase the range of their weapon systems considerably, including SBs. I think it would be cool to make it so that eventually, the range of your weapons could be double from what it was at the start, but the farther away from the target, the increased chance to miss, and perhaps less damage. Less damage for beam weapons, increased chance to miss for projectile weapons. This would take play testing to figure out. I don't like the way though that missiles in space have a limited range b/c in space there is no gravity and once a missile starts moving, it shouldn't stop unless something stops it. A missile could run out of fuel though and stop manuvering, or it could be jammed.
Also, I think things like beam weapons should do damage per second as opposed to a strait shot damage and the amount of damage done should be for how long the beam actually stays on the enemy ship, making it so that if the beam is on the ship longer, the ship takes more damage. The banks that move beam weapons though should be slow resulting in if a ship moves quickly, it would be able to dodge the beam weapon...(this is a game play change and my not be possible in the current game)
For the Titan class ships, I am hoping that these are really cool and usefull ships, however, I hope that we are not getting deathstars, war suns, terror stars (choose your name)....yet. I want them, however, I feel that death star type ships are a step above what I am imagining titans to be so I am looking forward to those.
That's it for now, let me know what you guys think. I think a lot of fun could be had with the espionage and electronic warfare tech trees. Espionage itself could probably be it's own mini expansion.