Is it possible to have the server to report the IDs of both the bountied target and the one who set the bounty whenever /bounty list is run? If so, this could prevent accidental scenarios where say, a pirate bounties a Freelancer and a Bounty Hunter makes the claim, which can't be done by the rules since it's an unlawful bounty. This would also tip people off if one member of an ID bounties another member of the same ID. Setting a bounty on an ally is sketchy, and would need a really good explanation inRP as to why they would want an apparent ally shot, imo.
I'm not sure about announcing to all of Sirius whenever a high-value target logs in. That seems like it would promote shadow-logging. That said, I could see the server announcing a message system-wide: "A highly wanted individual has entered the area. Caution is advised." whenever the bountied target enters a system via Jump-Gate (I'd imagine TLAGSNET would be inRP responsible for reporting that). Entering a system via Jump Hole would not trigger this message, as Jump Holes are natural phenomena. This would encourage bountied targets to try and lie low by avoiding Jump Gates. The system-wide announcement would only play when the target themselves jumps into the system - Simply jumping into the system that they are within will not alert the player.
I also like the notion of bounties having a maximum duration. This would allow a bountied player to lie low for a while in order for the "heat" to die down. Is it possible to set it so that high enough bounties have a higher maximum duration/no time limit? I've seen bounties upwards of 50,000,000 here and there (including one or two back in the day that the Reavers were pretty quick to jump on for 100,000,000!). I doubt that if someone was willing to pay that much for someone's demise, they would want that person dead, no matter how long it takes.
A processing fee is neat, plus to me, it makes sense inRP. If you want to avoid that fee, post a forum bounty!
Final note and idea: Add a /checkbounty command that allows you to check if the player you have targeted has a bounty on them. Shorthand for the command could be /cb . This will allow Bounty Hunters and Freelancers to check a target on-the-fly rather than trying to go through Sirius' entire list of bountied targets while tensions are high.