As co-owner of one barge, when I think about future of it, this comes to my mind:
Barge should be prevented from using in jumping. It make too much mess in economic system when just two people can powertrade very effectively. This solves main part of problems which are connected to barge in these days. By the way barge jumping moreover doesn´t make too much sense inRP. Jumping ship (typically Zoner carrier or juggernaut in these days) is with strongest jumping device making a field of some size (which is little bigger than this ship with the strongest device). It makes sense that transport which is smaller or similar size in compare with jumper can be within this field so it is "dragged" with jumping ship to new location. But it totally doesn´t make sense when barge which is several times bigger than jumper, can do this too. Such a huge ship can´t just be co-jumper. Maybe devs can think of jump drive Mk V only for barge, which will take 20k of cargo space and 15k of fuel for one jump when charging will takes 15-30 minutes. So it can be used for barge movement (so people don´t have to survive that pain moving through big asteroid fields) but hardly for powertrading.
Of course, barge should be of course also prevevented from using trade lanes, real nonsense. Because even despite model changed it is still possible.
What I would like to see (and other people said it there too) is more barges just flying around because it is amazing view to see them similarly to supertankers in our world. To encourage this, barge should be playable by single player. Why not, when he can´t powertrade (you can´t really powertrade with barge after last speed nerf, by selling ore in 5k transport you make more money per second of flight with lesser risk, not speaking of pain of docking on some stations). For this, barge need better protection against NPCs which can be pain even friendly, not speaking of one hostile NPC which you can´t shot down without help because current transport turrets have too short range. Solution is simple, just give it special turret with longer range (doesn´t even has to be really strong) which can´t be mounted on other ships. If it is too complicated, just give it few cruiser slots (lighter class 6 only). It is still not enough protection against players, but enough against NPCs and this is like what it has to be.
After that I think more players will fly barges around and not primarily for money but for RP encounters and feeling of flying with this giant, attracting attention of other players shouting "wow!" And that is how barge should be used, don´t you think?