hmm, im not so sure about having to choose between anti-SC or anti-ship... but i definitly like the idea of flak weapons for Starbases... there is no reason why not these are massive structures... even if the range is only slightly greater than the diameter of the starbase itself (say, 5-10% greater?)
Pros/Buffs
Enables anti-SC protection so unless there is a shitstorm of them, you cant take out a secluded SB with a 1-2 dozen Strikecraft
slightly better damage output than TEC hangars or flak frigs
Cons/Nerfs
Each bank could have a very small firing arc to limit its effectiveness (though this would be balanced by having a larger number of banks and locations)
Require research to deploy (1-2 levels?)
Very short range
Cannot target other ships
Visuals
Imagine an Argonev with 6-8 streamers of anti-SC flak fire tracing up and away from the Starbase (imagine the first Wraith attack on Atlantis (from Stargate: Atlantis))
i think it would be very cool and useful. Honestly, if you have a whole crapload of SC, these upgrades wont matter that much, but it will stop someone from sitting a few carriers in a GW out of range of the SB and leisurely taking it down. as it stands, you either have to build at least 1 hangar upgrade, or station flak frigs at every SB without hangars maxed. i really dont see these upgrades unbalancing the SB too much