[MaxOMan]

Actually, even a medium transport makes a pretty decent auxiliary carrier. Since the "aux CV" doesn't need to be used in combat, it only needs a very few fighter bays (to launch fighters in case it gets trapped into combat).

Otherwise, just max out on cargo bays and you can carry A LOT of extra fighters. These make for quick resupply of your carriers after a battle, especially if the carriers are in a forward area fighting away from your planets. Thus the "aux CVs" can be used as excellent ferries to move replacement fighters to the front, keeping the carriers on the front lines.

Makes for kind of a WWII feeling with supply lines and all. I kind of like it myself.