I enjoy playing GalCiv2 so far, but there are some aspect where it could preform much better.
Let's start:
1. SHIP COMBAT - the ability to have some degree of control over the battle (could be researched - like Remote Field Command tech). Something like in Birth of the Federation.
Basicly you can select a single ship, all ships of the same class or a group of ships that fit the same category (command ship, scouts, fast attack ships, assault ships, non-combat..) and then give them general orders (flank, circle, ram, evade, strafe, chase,...) and then select the target (or target group). Click go and the battle starts with the ships trying to follow the orders the best they can. After 10 or so seconds the game auto-pauses and you can change orders.
Simple and effective.
Allso, weapon normals are a must. Let the ship fire when their guns are alligned with the target. Tuurets track and fire.
2. WEAPONS - too plain and not diverse enough. and hte division is bad. It should be devided into ENERGY WEAPONS (Laser, plasma, etc....), MASS DRIVERS and MISSILES. So what's hte differense you ask? The difference is that laser and plasma are DIFFERNT weapons, with different pros and cons that are researched independently. For instance, lasers have long range and high accuracy (due to their speed), but low damage, while plasma is devastating but has short range. Allso energy weapons aren't beams by default, they can allso be pulse weapons.
Let's deepen this a bit - ability to create your OWN WEAPON. How? Well, you research a tech..let's say plasma. Now you want to make a new weapon next ot the default opnes you get. You get a screen where you select the base weapon type (energy, mass driver, missile), sub-type (laser, plasma) and delivery system(beam ,pulase) and then you get displayed it's stats - range, accuracy, damage, size, power requirements, rate of fire...And each oif this stats you can increase or decrease with the + and - icons. The more you increase the stats, the more costly the weapon becomes and the longer it takes to build it and mantain it...needles to say it increases allmost exponentially. The more - you put in, the price goes down....Auto-balance.
Next you select it's apperance (normal and turreted) and give it a name and then you get to research it and later use it:D
One more thing to add is the abiltiy to actually have turrets and fixed weapons, and for that to matter in the battle.
So when equipping a ship you select if hte weapon is forward fixed, is it a forward turet (90° fire cone) or one of the full turrets (180° or 270° or 360°).
Next you select it's mount. The bigger the mount, the more space it takes up, but so does it deal more damage. Same for smaller mounts.
3. SHIP PARTS - more of them...lot more...and maby give all races acess to all standard hull parts (the cockpit parts).
Allso, the ability to encase a engine, so basicly changing it's appearance to something more armored and rugged looking..
4. RESEARCH - Alliances and Trade should be available from the very begining. It just doesn't make no sense that I can't make a alliance or trade with a race I'm good friends with. Especiall since I can build mammoth colony ships, so freighters should be very simple. the same could be said for transports..you shoudl get the earlier...
To connect with the weapons thingy, if you research energy weapons you woudl get 3-4 new options - plasma based weapons, lasers, tachions, etc.. Increasing level in each of them would give some bonuses to the basic design. And I'm not talking just size reduction - it can be anything - from rate of fire to damage to range to size....
Some racial specials would be nice - special tech that once researched can be implemented into ships or weapons...for instance - focusing cristals or gattling technology. So if you have gattling tech as a special you researched, you can design your new plasma gun and add the gattling special to it for drasticly increased ROF (for a substantial cost)
5. BALANCE - we're dealing with to osmall a numbers.. bigger numbers = more room for differences and balance. Increase HP of all ships 10 fold.. a hp ship becomes a 60hp one. Weapons would allso get an increase so more subtle differencs can be achived. the armor shoudl be implemented differenlty - when giving the ship armor you select the thickness - light, medium or heavy - and hte size, protection factor and cost are adjusted accordingly.
Smaller ships should be faster than large ones, and their speed and agiltiy should be their asset. Simply link the engine speed with ship mass. Smaller ship = less mass to push = more acceleration

This will make smaller ships usefull in battle as they will avoid getting hit and try to flank larger ships.
6. MORE DIPLOMACY OPTIONS - non-agression treaty (both nations recognize teritorial borders..AI will not try to colonize your planets), Research Alliance (BIG research boost), AFFILATE (your ships can go into orbit of your affilate nad use their starbases)
I got more but don't have time to type it all down now....