I haven't played any of the Tactics games and I've only watched the story of Tactics and not the Advance games yet, but I made my research on this topic.
So, from what I gather in the other races wikis, the "unique playable character" is actually someone relevant to the plot, like Shara, or Montblanc, and basically the ones listed on the Final Fantasy Tactics Advance wiki in the "Playable characters" part. That said, there's no bangaa listed there, so Pallanza must fall in a different set of playable characters that's not the "unique playable character".
Hope that clarifies a bit. Still, you're better off waiting for someone that actually understands this. Or perhaps try to create a Talk page about this with someone to get a quicker response.
