Broken Hawk
Emperor
Could another Civ be added to counter the Lithuanians should they be too powerful. The only one I can think of would be the Finns... but were they too primitive to really be nothing but barbarians within the sheme of this mod? I suppose we could add a Crusader state like the Teutonic Order, as well, which actually fought against the Lithuanians, but they may have been too far west to have any real effect in keeping the Lithuanians tame.
I've not yet playtested sufficiently to see some of the items you've mentioned as far as play balance, Drtad. I'm not certain how these can be addressed... could helpful resources be added near Byzantium while some be taken away near Lithuania?
Historically the Teutonic Order and Lithuanians were constantly at war, especially over the region known as Samogitia. Neither held on to the territory before the other would retake it.
The Finnic Tribes were very weak because they were caught in the middle of a struggle between Sweden and the Novgorod Rus who were fighting over the fur trade in the region.
At the height of Lithuania's power, it controlled lands from the Baltic to Black Sea.
Now with respect to balanced gameplay in EMA, I think Drtad is right and potential access to resources should be tweaked to give the Byzantines a fair chance.