The simplest solution: remove the line that allows a FL ID'd ship to claim blanket bounties. It will still allow freelancers to take on-the-spot jobs while returning the heavy bountying business to the actual bounty hunters. Yes, some unlawful factions might lose their bounty boards but that's just a sacrifice they should make for the greater good, unless the Mercenary ID is brought back.
Also, remove or nerf the mining system. As I said in another thread, the easy money made thru mining is killing all other aspects of Disco's economy, bounty hunting included.