I'd want montblanc and a bangaa of some sort. So probably Monid since there arent too many good notable ones (except Ba'Gamnan but I mean come on).
It disappointed me that the only non-hume in FFXII we get in our party is Fran. I loved encountering the Bangaa in the ester/westersands and would have loved one in the party.

Montblanc is just a badass so that'd be fun, hes such a bro in FFTA2.

I quite enjoy using Penelo and Vaan in combat though with self-imposed jobs (Penelo as a "monk" and Vaan as a "magic samurai").

But yeah, I'd trade them for any non-hume characters~