Point buy?
I think you can pick almost any class and have this work. You really just need Firearms proficiency and a high Use Magical Device skill (or Use Technological Device, depending on your campaign setting) and start making a collection of fun "bounty hunter-esque" weapons and toys. The feat Create Wonderous Item would help you save some money in this endeavor, and it would allow you to work with your GM to custom create your own items if you can't find a specific wondrous item that does what you want.
As for the Mandalorian's armor, you'll probably want to pick a class that can use Half-Plate, or at least dip 1 level into a class that can do this. You can start with Steel armor and eventually work your way up to Adamantium (Beskar). Half plate is traditionally a mix of Plate and Chainmail, but you can substitute the Chainmail for Leather for thematic reasons.
Honestly, Gunslinger might be your best choice for primary class, but you'll need to dip a level in Fighter (or w/e) for the Half-plate proficiency.
If I have to pick one, I'll say it's Far Strike Monk.
1. Lawful, so you know he follows a bounty hunter's code.
2. Proficiency with ALL thrown weapons. Dire Bolas, Grappling Hooks, Lassos, Nets, Shurikens, you name it.
3. Still able to get Qinggong Powers, so you can mix it up with ki spells!
4. Stealthy shooting!
5. Able to chase down enemies while shooting!
6. Can shoot THROUGH WALLS.
7. Quick Draw to be the fastest gun in town.
If I have to pick one, I'll say it's Far Strike Monk.
1. Lawful, so you know he follows a bounty hunter's code.
2. Proficiency with ALL thrown weapons. Dire Bolas, Grappling Hooks, Lassos, Nets, Shurikens, you name it.
3. Still able to get Qinggong Powers, so you can mix it up with ki spells!
4. Stealthy shooting!
5. Able to chase down enemies while shooting!
6. Can shoot THROUGH WALLS.
7. Quick Draw to be the fastest gun in town.
What about wearing half-plate though?
Bolas are pretty awesome for Bounty Hunters (don't necessarily want to kill your quarry). Flinging Charge, throw a bola and trip your target, finish your charge by pulling out a weapon (either a non-lethal weapon for subduing, or a real killy weapon to finish them off since they should now be prone) mid charge and wail on them. Cudgeler Style could be useful too.
Bounty Hunters in the Star Wars universe do indeed use bolas.
because EVERY main character in the movies at some point gets captured.
The slayer actually has an archetype called Bounty Hunter. There's no reason it can't be ranged either, so that's certainly an option.
Bounty Hunter Slayers lose too many features to combat maneuver features that are a bit hard to get good advantage for.
What about wearing half-plate though?
I was going for function, not so much looks.
Too many features? You just trade out 3 talents. You also gain proficiency in things like nets and bolas. It’s really rather good for a ranged build.
Bolt ace gunslinger switching between a slavers crossbow and a standard one, alchemically enhanced bolts (tangleshot, slowburn, etc..) for special occasions.