I really think this is a good topic and I hope the Dev Team does considers changes (yes, I know they are still working on combat). Many good and valid comments made here on topic but IMHO star base offence/defense is broke.
Built up a Mil starbase in stages to A-18/20/19, D- 23/63/25 and gave it to the Drengin. Took a single standard Ranger missile ship A 0/8/0 D0/20/0 (shortest range weapon?) and attacked 5 times (kill/reload). Ranger won every time taking 0-45hp in damage. Repeated with a Frigate 0/9/0; 0/0/19 and got basically the same results, frigate won every time.
While I agree with many commenters wrt. not making starbases super powerful, right now it just not seem worth it put any off/def upgrades on them. (Actually does work as deterrence to the AI, but if attacked you will die). Seriously, how can anyone justify a 0/8/0; 0/20/0 ship having NO problem with a A-18/20/19, D- 23/63/25 Starbase? As I said .. Something is broke.
Should SB’s get to fire at enemies in AOE? – No way
Should SB’s be super war machines themselves? - No
Should SB’s upgrade upgrades work better? – Absolutely (and I do believe SD is working on it)
Should spamming fighter be the only way to defend SB’s -No
Should a stationary defense be less efficient than a mobile one? – yes .. but by how much?
Should SB armament be relevant (more than just an AI deterrent) ? – Yes or get rid of them