I think Balthier would definitely keep his ear to the ground, both for the reason you said and to keep an eye on what his father is up to. He may claim not to care about politics, but I think that it's an act, at least in part.

I do remember the mines being good for money and levels, and right now I could use both, especially the former (spells aren't cheap, you know!). But I also needed to do some leveling while trapped in the Leviathan -- I lost pretty badly to Ghis the first time I tried it. Does the game go on rails after Leviathan, or will I have some time in Bhujerba before I have to run off to the next place?