right, the combat advantages are not nearly as big a deal as they would be on a ship you actually want to deploy in battle. i just think it shouldn't have those combat benefits and significant campaign benefits. the fuel capacity is probably the least of those, but 500 less cargo capacity also isn't really a big deal when you have a fleet with superfreighters.
as for real combat freighters, i'd like to see more of those in general as well. but military transports (ships that are still dedicated freighters/tankers/troop-transports, but with miliary grade hulls and systems) also fit well into the sector, i think. having ships that are cheap to manufacture and maintain is important, but so is having ships that can properly defend themselves in an emergency. the major factions, including the Independents, could even have dedicated military transport fleets, designed to break through blockades, or to operate in systems with high pirate activity or open faction hostilities.