with each hull technology there could be a new module that adds hit points to the star base.
More modules is assuredly not what starbases need, especially since balancing starbases with ships under the current model is a fool's errand; you cannot do it because you cannot know how powerful the ships will be at most stages of the game. By the end of the game, one player could have +70% hull capacity due to specialization choices, another might not have taken any of the bonuses to (effective) hull capacity, somebody else could have gotten sort of vaguely lucky and used tech trading to acquire every last hull capacity bonus and component size reduction in the game for an effective hull capacity bonus of something like +300% (probably more; looking through the Terran tech tree, you can get up to a 70% reduction in weapon and armor component sizes, a 60% reduction in shield, point defense, drive, and sensor component sizes, and a 25% reduction in support component sizes, as well as a 70% increase in hull capacity from technologies). And that's just from technologies that directly affect effective hull capacity; this isn't considering the Hyperion Shrinker (which, with only a moderate amount of level stacking, could easily be granting around +50% hull capacity on its own), Helios Ore (which might not seem like much at +5% per resource, but it can add up, particularly on larger hulls or with stacked component size reduction techs), the Design Revolution event (+10% hull capacity per event, with the only 'drawback' being that you need to take Malevolent ideology points with each bonus), the empire bonus you can take at the start of the game for +10% or +20% hull capacity, and maybe one or two other things I've forgotten. Starbases, meanwhile, have a very fixed set of potential builds; outside of a handful of techs that provide bonuses to starbase defenses (while providing the same bonus to ship components of the appropriate type), there is nothing in the game which can affect the maximum strength of a starbase. Just try and balance that against ships whose power levels are as wildly variable as this game's ships are. Then realize that hull capacity is just potential power, and as wildly as the potential power of a ship varies, the actual power, being dependent upon how the ship's hull capacity is actually spent, varies even more wildly - you could have ship A with attack/defense scores of x/X, y/Y, and z/Z, and ship B, with twice the (effective) hull capacity of ship A, may have exactly the same attack/defense scores (thus being no more powerful in any given engagement than ship A) despite having twice the potential power due to having twice the effective hull capacity, while ship C, which like ship B has twice the effective hull capacity of ship A, has twice the attack and defense scores of ships A and B put together (but perhaps gutted its drive systems to manage this, and so while it's incredibly powerful in any given engagement, it isn't a particularly powerful unit overall because it's just not that mobile).
This is a major issue when it comes to discussing the 'balance' of starbases against fleets, because especially by the late game (when starbases are at their most costly, due to the irritating feature of having to build every single obsolete module in order to get the state-of-the-art modules that you want) a ship can trivially be several times more powerful than the baseline ship strength would indicate. What opposition do you want the starbases to be balanced against? I guarantee you that a Huge-hulled ship which has the maximum bonuses to effective hull capacity that its designer could get for it and which spent that hull capacity almost exclusively on weapons and defenses presents an enormously different threat profile than a Huge-hulled ship that has the same bonuses to effective hull capacity but spent about half of its hull capacity on drive systems at the cost of weapons or defenses, and both of these ships present enormously different threat profiles than a Huge-hulled ship designed by a player who didn't stack the effective hull capacity bonuses and so has a much more limited potential power even if the hull is packed with weapons and defenses to the exclusion of all else.
I would say that the best thing that could be done for starbases under the present model isn't 'balancing' them to be competitive with an equivalently-advanced small fleet (because good luck with that, what with how variable ship strength can be), but rather reducing the number of modules that are required to fully upgrade a starbase.
