One thing you have to take in mind is the design philosiphies of the different intersteller powers, and the reasoning behind those schools of naval architecture. There is a reason why fighter designs are more prevelant in one government then another. There is a good reason why the Federation decided a while back that Fighters weren't a good idea. With the trillions of people that the Federation has (and lets not take into the account he real CGI model cost reasoning), don't you think that the idea is supported somewhere?
The reasonings why fighters were created out of the Peregrine Couriers during th Dominion War are logical, even if you aren't presented with them up front in the TV Show. However, that is not to say that the concept isn't without merit. And that isn't to say you wouldn't see Civilian to Military converts during those difficult times. But at the same time, you have to think about how far they would modify a vessel . . . as I am sure that there was a reasonable expectation for the ship to return to its civilian/peacetime owner and purpose eventually. Therefore . . . going as you suggest, unless you design a purpose built escort carrier . . . I would suggest you design a reasonable large sized cargo vessel first . . . or take one of the prebuilt ones . . . like the one from the ICON Players Guide . . . then modify it to an extent that would allow for it to be used to carrier fighters.
Maybe you wouldn't have to modify the whole ship, maybe just create a purpose built cargo pod which can carry/launch/land/service the attached fighters.