Just wondering if it would make sense to add religion to the mix... ie, reduced cost and time for saians to learn eldari, odarians to learn battle, etc. I'd leave out setites getting discounts on caneer because (1) that's already not allowed, and (2) I can't see thieves permitting even Setites to learn the language. Kressa would murder any thief she found out was teaching Caneer to non-thieves, citing it as a threat to all thieves, everywhere. What if that person then taught another? And so on.
KT