We used an Activated Blackstone Fortress for the first time in a recent game. Here's what we came up with:
We decided that the ABF uses the standard ship critical hit table (not the planetary defences table) - the 'Defence' category just makes it easier to hit, like an Ork Rok.
We decided that the critical hit chart should be modified as follows:
2-5 (any 'Armament Damaged' result): Reduce warp cannon Strength by 1 until repaired. (So if the ABF takes a 'prow damaged' and a 'starboard damaged', it will only have Str-6 warp cannons until repaired.)
6 (Engine Room): +1 dmg but no other effect
7 (Fire): as normal
8 (Thrusters Damaged): Cannot move until repaired; +1 dmg
9 (Bridge Smashed): No longer auto-passes Ld checks. Instead must use Ld 10. Cannot be repaired. Possible adjustment: Extra 'Bridge Smashed' results reduce Ld by 1 each. This prevents the damage from moving up the chart to Shields Collapse.
10 (Shields Collapse): as normal
11 (Hull Breach): as normal
12 (Bulkhead Collapse): as normal - during the game a nova cannon hit did nine points of damage thanks to this...
One other result we would have liked to add to the chart is a "disables super-mega-death-shot until repaired" result, but I'm not sure where to fit it in, and it might be too effective to include.
We also noticed that as the ABF automatically passes all Ld tests, it can a) snipe targets and b) disengage whenever it likes. This seemed like a fair trade for it being unable to brace for impact. You have to kill it on the same turn you cripple it, otherwise it's certain to get away (unless it suffers the 'Bridge Smashed' result above).
BTW, we treated the warp cannons as lances that ignore shields (so hitting ordnance on a 6). They're a bit less useful than they seem on paper, since the ABF can't lock on.