I put, "Nothing needs to change", because I think the Fortress concept itself is currently broken. I think we can come up with something a lot more interesting and intuitive than the current method of "obliterate anything but bombers", so I'm holding off any votes on Fortress-related things until something is done about that.
I might start a thread about that soon(TM).
I didn't vote, but I'm with you on this one, Wingflier. I look forward to seeing what you come up with. Here are my thoughts:
I feel that the role of the fortress should be against heavier ships--that seems to be the weak link in the 'vanilla' defenses. I'm thinking Fortresses base damage should be reduced with bonuses along the lines of 0.2 Polycrystal, 0.5 Artillery, 2 Heavy, 2 Ultra-Heavy, 2 Command-Grade. That way, Fortresses would be less effective against ships in general, to keep the response from being completely binary. The Fortress would not do as well against Bombers and Artillery, which makes sense. Heavy and Ultra-Heavy naturally fall into that role. And Command-Grade is a much-needed bonus for defense, especially since most turrets have a multiplier of 0.1 Command-Grade (the only exception I know of is the HBC, which doesn't have multipliers). Obviously, these numbers will most likely need tweaking by someone better at balance than I am. I could also see giving Fortresses Command-Grade armor--it fits lore well and makes it so that a Fortress is a little bit tougher defensively.
Also, Fortresses should be immune to Radar Dampening. I took out multiple Superfortresses in a FS game using Space Planes...if it wasn't for Guards/Ion Cannons, I wouldn't have lost one Plane. That's just plain silly.
The Superfortress could get a few other perks for its cost and being a Mark V unit--increased range, higher-than-expected stats, better multiplers, or a new ability of some sort.