Two ideas that were central to Galactic War's previous design were credits and player assets:
Credits would be obtained from player actions and from territory control. ie, 5 credits for attempting to defend against an enemy attack, 5 credits for defeating an enemy, 2 credits per planet under you control, per day. Credits would be used to perform other Galactic War actions, such as attacking (5 credit cost), or using special abilities, like firing the black sun to make UEF the victor of the Galactic War (1000 credits or some such).
Also, credits would be utilized for persistent player assets. What are those? Essentially, they are mobile forces that can deploy with a commander to attack a world, and/or a base that the commander can use to defend a world. Persistent player assets would work like this: For a small cost (say, 2 credits), a player would build a small outpost (1 land factory) on a planet they own. They would have the option to upgrade this for additional credits (3 credits to add 2 mex, 2 pgens, and a T1 radar) with diminishing returns (benefit per additional credit). This base would remain on the planet it was built on until the base is attacked. Any player on the faction of the player that built it could use the base in a defensive action. IE, another faction attacks that planet, the defender starts the game with that small base.
Attacking forces would work similarly, but have two separate costs: Construction and gating. For example, 1 credit would build a small raiding force strike group (2 scouts, 3 tanks) on a planet controlled by the player's faction. Like bases, strike groups can be upgraded, with diminishing returns. For 1 additional credit, the player could gate these forces in, along-side the commander in an attack. In this way, asymmetric battles can be created, potentially with low-skill players (who strategize in GW) defeating high skill players (with a weaker GW strategy).
Also, to prevent the snow-ball effect of invincible bases or strike forces eclipsing everything else in value, actions with or against persistent assets will always damage them. For example, if a level 1 attack is a lone ACU, and a level 7 attack is an ACU with a tech 2 strike force, a defender with a level 14 base will always take 7 levels of damage, even if the attack fails. Thus, a level 14 base would be reduced to level 7. If a level 7 base were attacked 7 times by lone commanders, and was victorious each time, it would still be destroyed unless rebuilt in-between battles.
Also, it should be noted that many months ago, Thygrr and I nearly perfected the code to put this in game, essentially allowing custom units to be spawned in, as determined by the GW server. This would allow players to customize the units/structures they want (tanks or artillery, pgens or mex) rather than forcing strict upgrade paths.