Let's play some Firefly, y'all!
I both hate and love you right now. I don't have the time to GM but could squeeze in time to play. Would also be up for helping do set-up and handle more of the squishy story stuff if there is a potential GM that enjoys the crunchy rules part.
There is a Firefly TTRPG, I dabbled in it when it first came out. It was...rough. However I have heard MWP has improved the Cortex system significantly since then. They also did the Supernatural and Leverage TTRPG. I don't remember if they did Desden Files or not.
I have heard Powered by the Apocalypse (PbtA) Scum and Villainy does a good job with the crunch. Of course, one could also freeform (I tend to freeform most these days). It would need to be a Mature but more likely Adult rated game. My preference is for Adult, personally.
I could see a game set in the ‘Verse as either being a rag tag transport ship, a crew working with one of the various criminal organizations, a band of Browncoats who refuse to give in and surrender, life on a station, or any other number of scenarios.