After reading over a few of your ideas I figured id put down a few of my own. Input is appreciated, especially if you can get through all of it

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Overwatch
As one of the other posters mentioned, employing a system that gives each ship a set number of action points per turn, allowing you to “save” points for use during your opponents turn would greatly improve the level of control that the user has over his units. It also gives rise to the creation of an ability based system, abilities costing a set number of action points before being used. This system is much like the one used in various RTS games such as warcraft III, company of heroes, and of course sins of a solar empire. This system could be implemented into the module system that exists for T.A. allowing the user to further customize their tactics.
Overmatch
When you or your opponent have a technological edge (i.e. speed, weapons range, targeting etc) it applies directly into combat.
For example, unit A has a movement of 4 and a weapons range of 5, unit B has a movement of 3 and a weapons range of 4, which would result in unit A being able to engage unit B at range without risk of retaliation. Factor in a random margin for error (pilot error, mechanical b.s. etc) and you have a slightly more complex and dynamic combat system.
While the Gal Civ 2 system basically does this using incremental increase in damage and speed, it only marginally affects combat. This is because speed only affects the order of attack, instead of providing control over the fight, i.e. the ability to engage and disengage at will. This also relates to weapons in that the race with superior targeting technologies can attack from further away (given that they have weapons that are capable of such an attack).
New L.O.S. Mechanics
Changes to the way Gal Civ 2 handles line of sight would serve to improve the number of tactical choices that the player can make, giving them more options to explore. By this I am referring to the creation of a stealth mechanic as well as adding further depth to the current system. To explain further, I would like to see the addition of an active/passive detection mechanic or a radar like system. This system would allow the player to choose between two types of detection mode for their ships, one passive, and the other active, one state would allow for more stealth but less visibility (passive), while the other would allow for less stealth and more visibility. Ships would have a base visibility value depending on their size and other factors (stealth enhancement modules/ anti-stealth). This new system would increase the tactical challenges and solutions giving the player, yet again more options.
Combat Changes
- Improved Visuals (of course we want these)
- More dramatic ship pathing, i.e. make the ships maneuver more, the current system is fairly clunky and all ship types move the same way despite size (speed is effected, bigger slower, but all ship types seem to maneuver the same way) mix it up a little.
- Countermeasures/Effects – if the ship has chaff, make it visible, using a P.D.S. fill the area with tracer fire, just make things look more chaotic and I’m sure the level of intensity of the fights will improve as will the immersion factor.
- Tactical Weapons – space mines, nukes, lazer net of death, whatever flavor they add tactical freedom and more ways to skin the cat that is gal civ.
- Pre-combat tactical choices – much like the invasion system, this would allow the user to pick a tactical stance before fighting.
Movement and Nifty Stuff
- Jump mechanic (movement idea 1) - allowing the player to spend money/resources to insta travel (with a cool down time to prevent overuse). This would allow for lighting raids but would substantially drain the users cash supply if it was overused.
- Active Spatial Phenomenon – i.e. nebulas, caustic clouds, comets – anything like this would add some terrain to the blackness of space limiting movement and or providing tactical advantages. (hide in nebula, comet has special metal etc) Simply put it would add variety to the lifeless void.
- Warp mechanic (movement idea 2) – not to be confused with movement idea 1, this idea centers around the notion that ships moving at warp move really fast and thus cannot turn fast (yea I’m no physics major here so bear with me). Basically put if ships use warp drive they move faster, but must move a specific distance and only in one direction (i.e. must move at least 10 spaces, while ships that use sub-light drives will be allowed more freedom of movement but will not be able to travel as far. This mechanic, while maybe not very realistic would allow for some increased tactical game play, causing the players to have to plan their movements and also allow them to setup choke points at various areas of the map that they expect the enemy to warp in from.