Is there a way to change where Episerver looks for the lang files? We have a couple of sites where we need the same lang files, and it would be perfect if we could just point the sites to the same lang directory.
Or is there another way?
No, but you could write some small startup code that programmatically "injects" language documents from your location of choice.
Check out the LanguageManager.Instance.LanguageDocument.Load() which takes a Stream to the languagedocument as its argument.
It would be beneficial for this to be in a shared location. I have tried using the overloaded constructor for LanguageManager. Which works in some respects, all labels are displayed correctly in edit mode. But default properties such as PageName are not displayed as their language specific alternatives