We just finished a 13 session run of a space set Apocalypse World game, mildly influenced by Firefly.  We ran with four players, all co-MCing, and I thought I'd share a few custom moves from my fronts.

First, the Garden Ship was a Grotesque threat inspired by the Lotus Eaters.  They lived off an alien fruit that had turned them into blissed-out freaks.
When you eat of the fruit roll +weird.  On 10+, you see things so clearly; ask the maelstrom one question and the MC will give good detail.  On 7-9, you feel fucking great and have a +1 ongoing to actions that get you more fruit.  On a miss, you come to a few hours later feeling unburdened... tell the group about something you love, and then forget about it (yes, forever).

For my Reavers, I broke them up into solitary, gang, and ship moves.
A single reaver has:
Don't Blink: If unattended, it disappears from any prison.  If attended and its keepers are distracted, roll +sharp.  On a 10+, it tries to escape, but you put it down.  On a 7-9, it attacks you, suffer harm.  On a miss, it's gone.
Reaver gang:
Blood in the Water: If space and fiction allows, should you enter combat with reavers, each turn sees their numbers swell in group size until the space is full.

I particularly liked how these threat/moves played out, and would love to hear how they work for anyone else who wants to run with them.

I played a Battlebabe with a hard +2 thanks to advancements.  I was given a gang by the MC thanks to my seductive badassery.  It worked fine until I left them to throw in with a slave trader who had a better chance of getting me what I wanted.  I traded up.