The only mechanic that could be used to persuade more people to play in open and that's to have a beacon to attract authority ships pretty quickly, (even if it incurred a small cost to call them in). How many arrive (and teh relevant cost) would depend on how many are attacking you. They are NPC's and no real match for a good pilot but would dissuade the cowards who can't put up a real fight against a real combat ship, plus it will give you an opportunity to escape while the pirate(s) are fighting off the NPC's, (or help the NPC's take on the pirates). Having a longer c/d even when you submit wouldn't be so bad then.
I like this idea. I'd go one further and allow the hiring of NPCs (price calculated by distance to target) as escorts. Have your own flying armed NPC escort. It'd become a challenge for the pirates. Want that juicy cargo? Well a T-7 or T-9 with something to lose will probably hire security. How badly do you want it? Badly enough to take on a wing of NPCs while trying to blow the trader's cargo hatch? He'll be running of course... Why wouldn't he? Trader's wouldn't feel quite so helpless and pirates get the action they crave.
Of course the 1.2 already allows this kind of interaction anyway, I'm just hoping it will be developed more. If its reinforced by the game perhaps it might even bring about the rise of combat escort services from other players. You could reinforce it the player interaction by adding a option to share a percentage of the net profit if they join a wing to be escorted. All predetermined by the players. Pirates would have to attack in a wing, and escorts would have to defend their prize. It could even develop the meta in some fashion, with "fake" groups of escorts making plans with the pirates to be attacked and then "run off" because they start "losing" for a share of the take. Traders making deals with pirates to lead bounty hunter groups in to an ambush for pirate revenge. Betrayal, drama, adrenaline and lots of laser scorched metal.
It could work. I hope it develops that way, but there's still one part of the equation that doesn't make a lot of sense. There isn't enough incentive there for the pirates besides PvP. They need more reason to do what they do, it has to be more attractive to go after the big score being escorted by a wing of dangerous bounty hunters than just his piffling cargo of 200-500k. Gotta make it more attractive! I haven't the foggiest idea how.