Freighters will never be a viable option for money making, simply because it is not feasible to use a ship with less cargo when you could use one with more.
If we want to make freighters useful, it's probably going to have to be an adjustment to their combat effectiveness, not how well they trade.
Buffing their power core in update 1 was a nice change, now some freighters can fire almost indefinitely with the best guns available - problem is, their lack of manuverability makes it difficult to use those weapons against fighters, and freighters are slow enough that bombers can hit them somewhat reliably with their energy cannons, which will destroy a freighter in seconds flat.
Freighters, IMO, dont have enough armor either - bombers and even some fighters have more armor than most freighters do at the moment, while freighters are all larger and slower. Buffing them up to bomber-level hull strength would be a small step in the right direction, in most cases adding only 2000-3000 hull strength to each freighter.
I think that all freighters need to be buffed up to class 9 gun slots and class 5 turret slots as well. Many freighters are like this already, but there are some, like the correo, which are simply lacking in firepower potential because they arent able to use the max level turrets or guns that their faction has to offer.
Even with those changes, freighters probably will not be used any more than they are now, though.
One change I'd like to see, though I'm not sure it's possible, is auto-aiming turrets. Most frieghters can fire their turrets 360 degrees, but fighting in rear view or turret view is not an option for a weakly armored vessel which needs to keep dodging. Most of their weapons, being fighter weapons, also need to keep sustained fire on a target to deal significant damage, rather than being high damage, low refire weapons like those on capital ships or even bombers.
If you could select a target and then have your turrets automatically fire at that target, regardless of if they're behind you or in front of you, freighters might finally have a unique combat style and be 'useful'. Most of the issue they have right now is not being able to keep enemies off of their tail, fighters and even bombers are simply too manuverable, but having auto-targetting turrets that can fire at enemies behind you would solve that issue.