JohnB:
It is a fairly complicated bit of code...
Even worse, you aren't addressing the fact that there are three major ways in which games treat languages and then even when in the same rough category, most games are very different in exactly how they works.
1 - Binary: You either know the language or not, no rolls, no muss-no fuss. Easy, this one is already handled by the RPoL system. This is how games like D&D work.
2 - "Skill" roll, you either successfully understand what is said or not. This is what Puckohue is referring to with his "45%", but very few systems run on a percentile. This is still basically binary in the system's rules... and changing it changes the way those systems work (but it's an interesting idea). I suspect this is how Rolemaster works?
3 - Affects Other Skills - Lack of understanding hampers communication and thus penalizes other skills (usually social skills). There is no 'binary' (understand/don't understand) or skill rolls or checks, being at a 'low' level in a language just makes your other skill uses more difficult and more fraught with failure. It could pretty easily interface with some "partial translation" system... but it's probably more work than necessary. This is how GURPS works.