The old cliche about the Holy Roman Empire is that it was neither Holy, Roman, nor an Empire. As other European nations like England and France slowly developed relatively strong national governments throughout, the HRE progressively fragmented in that period, with more power going to local nobility. Arguably, the Empire had ceased to exist as a meaningful political institution long before Napoleon made it official.
So, how could that have been prevented? What's the latest point in history that a Holy Roman Empire consisting, at minimum, of most of German-speaking Europe, could have turned around the process of political fragmentation and developed into a strong nation-state in the same way that the United Kingdom and France did?