How about a "piracy contract" enforced by a game mechanic?
This would be binding on both parties:
- Pirate makes an offer, give me X number of your cargo Y (if scanned, otherwise free choice for victim), and you are free to go.
- If victim accepts, they must eject cargo per offer. The cargo is not regarded as stolen - since there's a contract, even if backed by potential violence. If they don't accept the offer - think they can win or escape - then we're back in the current mechanic.
- If pirate breaks the contract and attacks victim, they receive a higher than normal bounty. Maybe cargo is again regarded as stolen since contract was violated.
A bit one sided but a good start.
I could see something like this:
-pirates and traders could be part of guilds, where pirates rank would increase based on non lethal encounters and traders equally on survived encounters as well, meaning traders would make a deal with the pirates. after all a dead trader in not a good trader.
1) pirate hoists flag and makes claims (these could/should take amount of cargo carried and only let pirate claim certain % of cargo)
2) as soon as this is done both the pirate and trader are locked into a contract and trader would be obliged to not spool FSD drive, log out... during a set amount of time and would need to jettison cargo
a) should both come to an agreement their ranks are positively influenced
b) one who breaks the contract takes a hit to influence
Having a positive influence should also have a meaning for both parties. Pirates could get higher pay on black markets, better missions from pirate stations, possibly some specialized gear or skins. Traders could get better prices on regular marked, better hauling missions, skins... possibilities are infinite.
Negative influence could for example mean higher insurance claims for the trader, higher prices when buying goods, where pirates would need to sell for lower prices, have higher repair costs or sustain higher bounties, possibly get more attention from NPC police and bounty hunters...