Yes, I know what Grand Duchy was, I was being sarcastic a bit because of your calling it 'Empire' :) The problem with this being, of course, that at the time of the mod, since 1385, Lithuania and Poland are in a union of growing closeness (from personal to total annexation). I don't think giving Lithuania a faction would be very historical, unless we want to play a 'what if', and toy with an idea of anti-union lithuanian nobles rising to power, and breaking the alliance. This has never happened, though.