So I've been working on a game for quite some time in a homebrewed world with all homebrewed races (well other than Humans) originally it was 3.5 but has since been changed to Pathfinder. Anyway, the game takes place in a renaissance/steampunk-esque world/era so there are flintlock firearms (with some homebrewed rules) and the world is made up of a bunch of islands.
Something I've been working on lately are the 7 pirate lords of the world. There is 1 pirate lord for each of the 8 seas excluding the south sea because the south sea is guarded by an aquatic race of humanoids (that the PCs can't play) that destroy any ship that isn't 1 of their own. There's also a bunch of other hazards in the south sea like sea monsters, dragon turtles, a bermuda triangle type thing, etc. etc. etc. The big thing I'm stuck on is coming up with bounties for the pirate lords. Originally I hadn't thought about it but I've been watching a lot of anime lately and thought, "o ya, I guess their infamous pirates who's names are known around the world." The other reason I'm trying to think of bounties is because I'm pretty sure 1 of the PCs wants to play a "wild west" type bounty hunter that uses flintlocks.
So far the pirate lords are like this:
Finsk Silvertongue - CN Zvaigzne Bard 14
Mugrow the Axe - CE Felgorian Fighter 13
Aigo Miguel - CG Human Alchemist 16
Madelin Madcap - NE Mudlark (Venerable) Druid 15
Jane Blackscale - CE Vahnthra Oracle (Waves Mystery) 12
Gwen Rochelle - N Human Ranger (TWFer) 12
Kaldarr Numondraad - CE Chittenga Rogue 8/Duelist 5
I'm assuming that the their level will increase their bounty but I guess what they've done would also effect it, for instance, maybe Jane Blackscale has destroyed more towns than Finsk Silvertongue so she has a higher bounty because although she's a lower level. I don't know, I'm just trying to think of reasonable bounties rather than saying something like o he's worth 5 million platinum or something like that.
Lots of stuff influences bounty, but from a realism stand point, the level of the villain is not one of them. A simple villain with a few levels in Expert could lay waste to half a countryside, while a 20th level villain might have grand schemes but maybe he's never broken the law (or at least, never been caught).
It's the villains' deeds that are the basis for the bounty (which you already alluded to). The more nefarious, destructive, and generally bad for civilization as we know it, the higher the bounty.
Also, some deeds might seem minor, but they piss off just the wrong person. Suppose Mugrow has murdered a dozen peasants but Kaldarr has only murdered one - but that one was a cute little assistant cook that usually kept the local governor warm in his bed at night. Which pirate do you think that governor will put a higher bounty on? Suppose two other pirates like to plunder merchant ships, but only one of the two has sunk a couple of ships belonging to the local lord's personal merchant fleet. The biggest bounty in the whole kingdom might be for the head of a poor innocent serving lad who accidentally exposed himself to the queen.
Another different factor is the wealth of the people posting the bounty. A wealthy kingdom can put up tens of thousands of gold to bring in a notorious pirate captain, but a small impoverished island nation might have trouble offering a few hundred gold for such a bounty.
Another factor is diminishing bounties. If one kingdom is constantly raided by all 7 pirates, they may offer a huge bounty for each of them. Why? Because all their merchants are going out of business, their navy is being sunk, they have no internation import/export, and their economy is being ruined. But once a couple of those bounties are claimed, there are fewer pirates, so there are fewer raids, and the perception is that things are getting better. The king isn't quite so desperate any more, so the bounties might lose some value.
Another factor might be how fast the bounties are claimed. If a kindom puts up 7 bounties, each for about 1/3 of their disposable tax income, and some group of heroes comes marching up to the gates once a week to claim a bounty, you can bet when their coffers are empty, the kingdom will lower their bounties on the remaining pirates.
None of which equates to game mechanics. If you want game mechanics, then consider this:
The Treasure Values per Encounter table says each encounter should be worth a certain amount of treasure. For example, a level 15 bad guy like Madelin Madcap, should be worth about 19,500 gp if you are going by the medium XP chart. But if you give her only 15,000 gp worth of gear, then you might want to set the bounty at 4,500 GP.
That's extremely simplified; Madelin probably has a whole crew of pirates that have to be dealt with, maybe a fortress somewhere full of guards and traps, and it might be a whole multi-session adventure to bring her down. When all is said and done, you should, according to RAW and this chart, figure out the total treasure of that whole place based on the CR of all the encounters, then divvy that out to each encounter. A magic weapon here, some potions there, some gold somewhere else, etc. What's left would be the bounty, mechanically speaking of course.
That's a whole lot of pain to go through. Me, I would just eyeball it based on my world story, who is offering the bounty and why, and how wealthy or poor I want my PCs to be.
And remember, some bounties may not be coins at all. Titles, lands, merchant charters, or other royal favors might be offered instead.
O, as far as the wealth of the people posting the bounty goes, the known world is made up of 5 islands/island groups, 3 of which have a treaty and are working on creating a "world government." Of the other 2 islands/island groups, 1 is a decent sized island known as Lasrien that is a snowy tundra type area but is pretty much completely lawless. The other is a group of 5 small islands known as Phandia that has a really weird form of government, it's almost like an anarchist set up (anarchy as in communities relying on themselves not Cid Vicious punching a mirror). Phandia will allow the Pirate Lords to dock but if they cause trouble the Phandian Circle (a group of eight 20th level Phandians) will deal with them. Lasrien is pretty much completely lawless so the Pirate Lords can go there and do pretty much whatever they want as long as they don't bad mouth "the Felgorian king."
The bounties I'm trying to figure out are the bounties posted by the alliance type nations. The Pirate Lords are supposed to be near uncatchable. Although the old Pirate Lord of the South East Seas was just killed by a group of assassins and in game he will be replaced by Kaldarr when the PCs get to a certain point (I don't really care about posting this because the PCs already know about Kaldarr from my notebook with the Pirate Lords flags drawn in it).
EDIT: As far as deeds go this is what I'm thinking: Mugrow's "armada" is known to raid towns and kill pretty much anyone, he has the largest crew out of any of the Pirate Lords, and he's a high ranking official of a crime syndicate known as the Axe Gang (think Kung Fu Hustle only with less guns and more axes). Finsk is probably going to have the lowest bounty but that's because he knows how to weasel his way out of things, I guess I can honestly say he's got an attitude kind of like Jack Sparrow only he doesn't perform random acts of good and he literally does everything for himself. Madelin is also known to raid villages and her crew is the second largest of any of the Pirate Lords, I'm thinking her bounty will be the 2nd or 3rd highest. Jane also raids places but she's also known for underhanded tactics (I've worked on her the least so probably a lower bounty lol). Gwen is really only a Pirate Lord because she challenges anyone who's rumored to be a good swordsman/woman, her crew is made up of only women and her and Hugo used to challenge each other to duels a lot because they both are/were extremely good with swords. Although Kaldarr is the newest member he's going to have either the 2nd or 3rd highest bounty because he used to be Hugo's 1st mate and is now the only living member of Hugo's old crew because when Hugo was assassinated the assassins destroyed his ship and killed all the members (or so they thought). Aigo (who actually goes by Miguel) is going to have the highest bounty out of all of them (I know weird for the only good aligned pirate lord but that's how it is), he's kind of like the Robin Hood guy in my world, he steals from the rich higher ups in the aligned nations then gives it to the poor all over the world (although he does keep some for himself), also, every member of his 10 man crew has a bounty on their head, they're the smallest crew but they're also rumored to be the strongest and the smartest "man" (who's actually a Felgorian) in the world is on his crew. Miguel is the only Pirate Lord that openly opposes the alliance government.
Treating the bounty as part of their loot is a good idea. I might let it go a bit above the value it should be, as collecting it might be an adventure in itself. The values of the bounties will also let the players have a rough guess of the pecking order of the pirates. If they decide they want to start collecting, they will probably start with the lowest one and work up.
Non-cash rewards (titles, etc) are another thing to reward to help convey the magnitude of the bounties without blowing the WBL guidelines. You can also give different bounties for different kingdoms. Barring etten pirates, they only have one head each. If one kingdom is offering 5,000 gold crowns for the head of the dread pirate, and another is offering the hand in marriage of a hot young princess and a title, you need to make a choice. It's also something poor kingdoms can offer. When your economy has been raked over the coals by pirates, you sometimes have to resort to offering up whatever you can to get adventurers to help.
Treating the bounty as part of their loot is a good idea. I might let it go a bit above the value it should be, as collecting it might be an adventure in itself. The values of the bounties will also let the players have a rough guess of the pecking order of the pirates. If they decide they want to start collecting, they will probably start with the lowest one and work up.
Non-cash rewards (titles, etc) are another thing to reward to help convey the magnitude of the bounties without blowing the WBL guidelines. You can also give different bounties for different kingdoms. Barring etten pirates, they only have one head each. If one kingdom is offering 5,000 gold crowns for the head of the dread pirate, and another is offering the hand in marriage of a hot young princess and a title, you need to make a choice. It's also something poor kingdoms can offer. When your economy has been raked over the coals by pirates, you sometimes have to resort to offering up whatever you can to get adventurers to help.
Ya, I have been thinking about title and things like that to kind of make up for the PCs only getting so much gold. Miguel is probably going to actually help the PCs out so his bounty is probably going to be irrelevant (although the bounty hunter PC may eventually go after him). I guess I need to start looking at gear for the Pirate Lords and things like that.
EDIT: O, on a side note I've house-ruled that a Duelist can use a pistol, hand crossbow, or other 1 handed ranged weapon and gain the bonus damage from precise strike if they're within 30ft of their enemy. That being said, Kaldarr uses a pistol with a bayonet on it (the bayonet for a pistol in my game functions like a dagger with no range increment).