It is not uncommon for me to use commercial hangars on some auxiliary carriers to carry fighters and FAC from system to system when needed. I usually also add some maintenance modules but not enough to cover the entire hangar capacity, just to prolong the maintenance capacity. If you take some parasites with a very low maintenance capacity it can be good to slow its clock down just a tad bit for longer voyages.
They can also be used for emergencies as small carriers in combat or extended patrol, but it would not be their purpose.
I do also have true auxiliary carriers who uses low powered engines but they have regular hangars, these are used for patrol and secondary jobs. They also can be part of larger operation in the rear formation, such as protecting the support element or troop carriers etc.. If I used fighters to bombard planets I probably would use them for that as well, but that is a bit too much micro to be worth it at the moment.
To comment on the OP... I would probably just put a resolution 1 active on a FAC and probably not bother with the passives at all. Passives that weak will not detect anything significant before your active does, most of the time anyway. You probably also will not rely their passives to detect anything... leaving a 10-15t passive can be OK just so you have something, unless you need those 20-30t for something else. On a 1000t ship there is not much room for luxury items. The reason for the resolution 1 sensor is to detect incoming missiles, you might be able to shoot one or two down if lucky. You also don't need more active than you have range of the beam weapon either. I suppose a ship like this will rely on other ships to guide them anyway with sensors.
