Up to 1700, hardly anyone would have bet on Brandenburg-Prussia as future unifiyer of Germany. Then, besides Austria, the princes of Bavaria, Saxony and perhaps even Hanover (Brunswick) had similar odds.
My personal favorite would be still a hypothetical line of competent native rulers after 1600 uniting and strengthening the conglomerate of the United Duchies of Cleve-Juliers-Berg(-Marck-Ravensberg). Perhaps even with a PoD in ~1540 allowing them to keep Guelders. Once some kind of Enlightenment leads to the idea of seculaization, they bag Cologne and perhaps Münster and Paderborn, and they are the by far most populous and most industrializable part of Germany.
My personal favorite would be still a hypothetical line of competent native rulers after 1600 uniting and strengthening the conglomerate of the United Duchies of Cleve-Juliers-Berg(-Marck-Ravensberg). Perhaps even with a PoD in ~1540 allowing them to keep Guelders. Once some kind of Enlightenment leads to the idea of seculaization, they bag Cologne and perhaps Münster and Paderborn, and they are the by far most populous and most industrializable part of Germany.