Well, Jewel Staite is known for Space Cases
and Stargate Atlantis
as well as Firefly
. But that's still short of superstar status.
Still, Staite is an odd suggestion for Nikki Heat. If you were limiting it to FF cast members, I'd think Morena Baccarin or Gina Torres would be more the direction to go.
I still think it would've been really wild if they'd actually made a feature film based on Heat Wave
and had the real actress starring in the film guest-star as herself in this episode.