Comprehend Languages would be cool. Some would argue that it makes a simple spell equal to weeks of work to earn a language ear, but I think it could be limited such that it would be acceptable. For starters, the caster can't speak the language, only understand it.
However, I understand that the language system is driven through listener code that's outside NWN, is hard to write, harder to debug, and seems to flake out for no reason from time to time. As such, it might be too much effort for too little payback.