I loved Firefly and shows like it. I’d like to throw out some ideas for folks wanting to play in their own ‘verse using the Starfinder rules as there are some things that Starfinder does by default that would be out of place in a low fantasy space western.
Races: So, do aliens live among us? Sure you could run your ‘verse as a humans only club, but I don’t see where having aliens in Firefly would necessarily ruin its character. Would Jayne be better or worse as a Vesk? How about Wash as a Shirren, Kasatha or Skittermander? How different would Inara be as an exotic elven princess or Lashunta? Would Kaley be better as an Android or Ysoki? Mal could be a gruff dwarf, I leave that decision with no judgement to the individual group of players and their GM.
Classes: Again not a lot of magic in Firefly though so you could run just the mundane classes. No Mystics, Technomancers, Solarians and some of the mundane classes lost class abilities. Only the Envoy is unscathed. I’m going to do a deep dive on Mechanics that aren’t Drone or Exocortex.
Skills: Without Magic, the skill Mysticism is probably the only one that doesn’t belong.
Feats: Without Magic, the following feats (and their lesser greater versions) serve no purpose; Agile Casting, Combat Casting, Connection Inkling, Harm Undead, Mystic Strike, Psychic Power, Penetrating Spell, Spell Focus, Spell Penetration, Spellbane, Technomantic Dabbler.
Equipment: You can have the baddest bounty hunters and vilest criminals in the black and they still carry basic guns and equipment. No matter how many times they say shiny, it’s not necessarily a story about gear.
The guns of Firefly can be covered by 4 basic semi-auto pistols (Holdout, Hi-Cap, Heavy, Magnum), and the same four revolvers, Submachine Guns, Silencer/Suppressors, Extended Magazines, Combat Rifles, Sniper rifle, Pump shotguns, Grenade Launcher, Hand Grenades. With a few exceptions most of the guns in the series are based on real world earth weapons.
“Six men came to kill me one time. And the best of ’em carried this. It’s a Callahan full-bore auto-lock. Customized trigger, double cartridge thorough gauge. It is my very favorite gun.”
It is my very favorite gun, can you imagine hitting a new level and Jayne drops Vera (This is the best damn gun made by man.) in a pawn shop somewhere or trades her in on a newer model? We’re going to give you 5 levels of firearms and some energy weapons which we will stretch across 20 levels of play by adding in extra damage dice as they become appropriate.
4 Revolvers, 4 Semi automatics, Azimuth and Corona laser pistols, submachine guns, a Mare’s leg, 2 Combat rifles, pulsecaster rifle, a sniper rifle, pump shotgun, double barrel sawed off coach gun, a grenade launcher, a heavy machine gun.
Shee-niou high-tech Alliance crap! In the series we mainly see scopes and laser sights, some bipods and extended magazines.
Five or so levels of gear,
“We’re gonna die.”
“We’re not gonna die. We can’t die, Bendis. You know why? Because we are so very pretty. We are just too damn pretty for God to let us die.
We are so very pretty, after you hit third level add your Character level to your KAC/EAC stretching the value of your first 5 levels of armor and alleviating the need for all characters to constantly be on a gear treadmill. Nobody likes grinding and in the show when the crew makes a big score they buy fresh fruit and new parts for the ship that desperately need replacing.
No power in the ‘verse, River has powerful Psychic abilities and badass combat skills, but there isn’t a lot of magic in Firefly. So while you could have Mystics and Technomancers and Solarians in your ‘verse you can probably get by with just Mechanics, Soldiers, Operatives and Envoys.
Other Cybernetics outside of limb replacements and Biotech really depend on if you’re playing in Alliance core worlds or not.
Computers, there are no Spell Chips in the setting.
Technological Item, the Regeneration Table and Unlimited comm unit are probably the only things too far outside the setting.
Magic Items, don’t exist in the setting. Hybrid Items, don’t exist in the setting. If your GM wants to let you rework your character you don’t necessarily need a Mnemonic Editor, just do a training sequence at your next level. Though with the kind of things they implanted into River a Mnemonic editor might not be too far out for the setting.
Only a few places that shuttle would make it to, the shuttles on the Serenity are Tiny in Starfinder terms mechanically, only require one crew member, and you can fit two of them on a Medium Transport or Heavy Freighter. The two shuttles are closer to a space Cargo Van than a Starfinder shuttle with 75 tons of cargo space. So you’re very likely to call the Serenity a Large Heavy Freighter and give it a shuttle bay that can hold two tiny ships.
Magic and spells don’t exist in the setting.