OTOH, saying "Saxony could become Prussia" is a bit determinist. Prussias rise was to a large part random happenstance. Theres nothing that says there has to be an east German great power.
I gave you Prussia as a German state that managed to smack down the Habsburgs and rise to the level of a European power.
Maurice could take most of the Brandenburg-Kulmbach territories, establishing Saxon power in Franconia. He could help the Emperor take back the 3 Bishoprics from the French (IIRC he himself had previously helped France acquire them) and be rewarded with one, 2, maybe all 3 of them, establishing Saxon power west of the Rhine. The Wars of Religion could still break out in France, providing all sorts of opportunities for an ambitious German Protestant ruler.
And the Electorate of Saxony doesn't end with Maurice. England will soon have a Queen Elizabeth and she may want to marry this time. The Dutch could still revolt, and in OTL they were quite willing to submit to a foreign ruler to protect them from Spain. An Albertine Wettin could later gain the Polish throne, after the last Jagiellon king dies (he'd have to convert to Catholicism, of course). The Czechs and Hungarians weren't exactly happy about Habsburg rule and I'm pretty sure their crowns were elective. And the Ernestine Wettins, who knows how they'll end up - it's a safe bet that some future elector will aim at reuniting the 2 branches.
I'm not saying that you can make Maurice into a Frederick the Great, but he could've built the base for a future Frederick the Great in his realm. The Great Elector, remember? Or maybe not a Frederick the Great, a better analogue could be Gustavus Adolphus or Stephen Bathory.