It is not as if the G created the power structure it codifies out of thin air. The Kurverein of Rhense near Koblenz in 1338 already was a meeting of the three Rhenish archbishops, the Count Palatine and the rulers of Brandeburg and Saxe-Wittenberg. Who patted each other on the back and confirmed that, yes, they were totes the guys who had a monopoly on electing the German King.
Even in the tenth century, the first four dignitaries from along the Rhine had had a elevated position among the imperial princes who as a whole elected the kings. The three "Easterners" joined them later for being quite influential:
In the contested election of 1198, a ad hoc committee of Cologne, Mainz, Palatinate and the Duke of Saxony was created.
Brandenburg has joined the others by mid-13th century.
So the lack of the GB would not change much poltically. Well, I do not not if it was earlier already forbidden to partition electoral lands among the heirs. If that law does not happen, we might see Brandenburg-Küstrin, Brandenburg-Potsdam, Brandenburg-Köpenick, Brandenburg-Tangermünde fighting over the electoral dignity.