Well giving that most if not all Sci-Fi universes have at least one type of monster cargo transport that are not capable of docking anywhere, and have to utilize loaders to fill its hold; option 6 is a sound choice. That said, since Barges have craft docks why not make it to where it permanently has a Loader craft docked with it that doesn't disappear once the ships offline (the Barge, not the loader). Now I have no idea how the coding and modding works, so I don't know if this is possible. But what if you made it to where a player can dock with the Barge then type a command line, transfer to the loader, unload the Barge, dock, then command line back to his/her original ship, or make it where they have to sell their ship to the Barge. The Barge then retains all of the ships equipment and cargo so that once the cargo transfer is completed; the player can then repurchase his/her ship at no cost to them. Of course, the easiest thing to do would be simply having transports dock with the Barge and transfer the cargo themselves. I just thought that it would be nice if the Barge had its own loading craft.
Option 2 shouldn't be done given that this is the reason that factions such as IC and GMG use them. Now option 3 might be a good idea given that the cargo reduction is kept to a minimum and the Armor is increased quite a bit. Option 4's a good idea but only if the impulse engines (sorry I'm a trekie) are brought up to at least normal speed but take a little bit to get to top speed, similar to the cruise engines that are already part of the Barge. Adding Jump Drive capability to Barges would be a great asset but, and please don't hate me for this, I personally think that jump drives should at least have distance limitations. Of course I've only made a few jumps with other players being the jumpers so I really don't know how they work. Option 5 is pretty much explained away in my option 6 argument in the first paragraph. Now for option 7, I think that if we were given an option of either a Barge Mk. I (reduced cargo capacity, increased armor) or a Barge Mk. II (increased cargo capacity, reduced armor) then this might be at least half of a good idea. Of course if you were to make it so that we have the option of cargo pods that Barges can carry, giving that it already looks as if its carrying pods, then we could possibly choose different capacity pods for it that could alter the Barges cargo Capacity and cargo options, as well as purchase armor up grades and make it to where a Barge can carry multiple armor upgrades giving its size and such.