Well, simply mirroring the events and results is rather implausible, since the Prussians overall had more efficient equipment, leadership and diplomacy. So the French would need to have sheer luck in turning chancy encounters to their advantage. A complete destruction of the German armies and a successful march on Berlin will not happen w/o ASB support.
One PoD might be a surprise success by French spies who uncover in early 1870 that the southern German states have concludes an secret alliance with the NGC and will not stay neutral or even rush against Prussia in order avenge their 1866 defeat. Far from it. So the French strategy might return to the Niel plan: a march on Saarbrücken, Trier, Koblenz and Mainz, or Sarrebruck, Treves, Coblentz et Mayence.
IOW, I do not think that the Prussian defeat will be so crushing that Bismarck is ousted directly - instead he will probably be able to achieve somne advantages, probably by pushing for a general European peace conference hosted by the UK (a thing he extremely opposed when Prussia was winning).
At the *Brighton conference, France as the victor will gain territory from Prussia - certainly the Saarrevier up to Trier, perhaps more. A further French aim might be the creation of an anti-Prussian South German Confederation, but it is unsure if that will happen. Demanding that Prussia give back Hanover, Nassau and Hesse-Cassel to their former monarchs and cede northern or all Schleswig to Denmark and the rest of S-H to the Glucksburg line are also possible. A rather fanciful idea might be the forced cession of the Rhineland and Westphalia to another German prince, who will be friendlier to France without being an outright puppet.
Of course, one could suggest an futher dismemberment of Prussia, with the Magdeburg district going to Hanover, the Erfurt and Merseburg districts to Saxony, Silesia to Austria and the Province of Posen to Russia, but that would be ASBish.
There will be certainly no German Empire, and depending on the severity of the Prussian defeat even the NGC might be dissolved. There will be no Stab-in-the-back legend and the military will probably get the full blame. Wilhelm I will resign and Friedrich III will become king nearly two decades earlier. He will probably push for an understanding with the UK. Queen Victoria will like that and the government might as well, when it has become obvious that France really is dominating the continent. In a more eastern Prussia, the junker class will be more powerful and for economic reason (the rivalry in the grain trade) they will also oppose Russia and favor the UK, because protecting the German industry from British imports is not important for them. Also, building a colonial empire and a big-ass High Sea Fleet is not where their interests are.