In Dropfleet Commander the AFB style defenses are abstract. They basically limit the maximum range of seekers/missiles/drones to the firing ships scan range (6" for UCM,Scourge, 8" for PHR and 12" for Shaltari). Any further away and the missiles are shot down before they enter range. Ships also have active PDF which can be used against each incoming volley of missiles/fighters to negate some of the damage.
For the randomization, I was just going to have check off a system box as usual and then once the damage is applied randomize where it goes. Given the damage limits, the players will have no choice but to mark one off a half weapon damage. It will let me get the feel of the crippling damage tables from DFC while still being quick and interesting.