My question is, what if medieval Poland centralized into an absolute monarchy around the fifteenth century, leading to less of an influence of the Szlachta noblemen and a greater chance of Poland becoming a belligerent force in eastern Europe? Would Lithuania be incorporated sooner, and is it possible for Poland to even score some victories against the Russian Principalities, particularly Novgorod?
Is it possible for Poland to become the eminent Eastern Slavic power (as opposed to a Russian state), maintaining an expansive empire from the Oder to the Urals, and eventually expanding into Siberia?