Could Wladyislaw III (spelling like Wikipedia does, anyway) have made a difference? Suppose he chooses not to break the 10-year truce against the Ottomans? (He was, reportedly, ambivalent about it.)
The problem, of course, is that they might have been attacked by the Ottomans later, but if they can withstand that, and he survives to have children...perhaps you have the creation of an alternative to the Austro-Hungarian Empire, and eventually, a Polish-Lithunian-Hungarian conglomerate that raises very interesting butterflies.They coud, at least, get to the Adriatic, and perhaps some African clonies later, getting them away from the Ottomans. (Polish Egypt would be a stretch, but a weird butterfly.)
Of course, it's hard to say how good this king would have been, considering he was only 20 when he died. In 40 more years, he could either have made the thing very strong and sturdy...or totally destroyed it.
The king after him did well enough, too, but if he's sort of the military part of a tandem, maybe they can do something; or maybe the POD is more around 1500. It'd have to be pretty early, though, yeah; though poland wasn't touched much in the Thirty Years' War, I don't know if they can really take advantge.