I'm not at home with access to all of my primary sources, but let me post some relevant passages from some sources that I have access to digitally.
First of all, it is not correct that the southern states in the war "gave up their sovereignity". The subjected their fighting forces to Prussian high command... that's all. They were still sovereign states. Their situation after the victorious war was exactly the same as before the war.
Okay, I hate to quote wiki but:
"Prussia and the other states in Northern and Central Germany united as a federal state, the North German Federation, on July 1, 1867. The Southern states Bavaria, Württemberg, Baden and Hesse-Darmstadt entered military alliances with Prussia. In the Franco-Prussian War of 1870–71, those states joined the North German Federation. It was consequently renamed to German Empire, and the parliament and Federal Council decided to give the Prussian king the title of German Emperor (since January 1, 1871). The new German Empire included 25 states (three of them, Hanseatic cities) and the imperial territory of Alsace-Lorraine. Within the empire, 65% of the territory and 62% of the population belonged to the state of Prussia."
States of Germany - Wikipedia
Yes, they were still states, but they had a new greater sovereign, Emperor Wilhelm I. Their situation after the victorious war was absolutely not like it was before. They were now part of the German Empire. They were now in a stronger commitment to Prussia and Wilhelm. They were part of an Empire, and not just an alliance.
The war created a climate better suited for the unificatio, but didn't provide "the stimulus, the means, the cause, the reason". Nothing about the war war relevant for the unification deals. Nothing about the questions the were part of the negotiations were in any way related to the war.
Yes, the war most certainly was "the stimulus, the means, the cause, the reason". There may have been other, of each item on that list, that were deeper (subjective) and earlier than each of those, but to deny that the war was not each of those things is not right.
Here is an outtake from Finnemore's History of Germany:
"During the course of the war a great step had been taken by Germany, a step to which her best thinkers and noblest patriots had looked forward for many, many years, the uniting of her states into a German nation. It was felt that as all the states were now joined in war to defend the Fatherland, so should they be joined in peace to protect it. In November 1870, while the siege of Paris was going on, Bismarck invited the representatives of other states to Versailles to confer on the subject of German union.
An agreement was made, and on December 3 the King of Bavaria, the chief ruler of South Germany, proposed that the Imperial crown should be offered to the King of Prussia as head of the new German Empire. William I accepted the crown on January 18, 1871. He did so at Versailles, in the great hall of the palace of Louis the Great, a hall hung with pictures of the victories of the mighty Napoleon, he who had destroyed the ancient empire, and amid the joyous shouts of princes who had but a few years since fought against Prussia : all were now united under one ruler and as members of one empire."
Yes, I think the war was the stimulus, means, cause, and reason. Yes, I don't think it was exactly the same for the states after that. This was pretty important, a turning point in their history, I think.
The unification, Bismarcks great project, had been in progress before the war, and included basically the same negotiations that happened during the war. Bismarck didn't wage this war to further the unification... he did it to remove France as a potential obstacle for the future process, however this might have been. He took the opportunity as it presented it... but he didn't try to create this opportunity.
Bismarck had indeed dreamed of and had been planning for unification for a long time. Now, you and I will never know why he did what he did. We have his Memoirs, which I would like to review on this when I am home. It seems a logical conclusion to me if unification was his great project, and this war accomplished it, that he did not just luck into that in the process of acting solely to remove France. If that was his only goal, he should have hit them harder after the war than he did, not easier as you recommend, which we will have an argument on later.
I am sure you are familiar with the Ems Dispatch:
"Bismarck took it upon himself to edit the report, sharpening the language. He cut out Wilhelm’s conciliatory phrases and emphasized the real issue. The French had made certain demands under threat of war; and Wilhelm had refused them. This was no forgery; it was a clear statement of the facts.[7] Certainly the edit of the telegram, released on the evening of the same day (13 July) to the media and foreign embassies, gave the impression both that Benedetti was rather more demanding and that the King was exceedingly abrupt. It was designed to give the French the impression that King Wilhelm I had insulted Count Benedetti; likewise, the Germans interpreted the modified dispatch as the Count insulting the King.
Bismarck had viewed the worsening relations with France with open satisfaction. If war had to come, now was as good a time as any. His editing, he assured his friends, "would have the effect of a red rag on the Gallic [French] bull."[8] The edited telegram was to be presented henceforth as the cause of the war."
Ems Dispatch - Wikipedia
Since you are obviously very studied in German history (no sarcasm intended, you are impressive). Then, how can you say, "he didn't try to create this opportunity"? Do you deny the details of this incident as related above? I can say that I have read variations on it.
The southern states did not want to join. They were extremely reluctant, and tried their best to gain as much advantages as they could. Basically they had to be bought off... won war or not. But they also knew that unification was basically inevitable. They had lost the support of Austria, they couldn't stay in the situation they were in - kind of second-tier Germans - and they couldn't rely on France as a reliable ally without pretentions.
Yes, because of all this reluctance, if not for the war the unification would not have happened. That was their tipping point. It was finally enough to overcome the hindrances that had been plaguing unification what seemed like forever. Was it just a coincidence that it happened in January 1871, at that point in the war? If the southern states could have been bought off, war or not, what a coincidence that was.
It is definitly not that "All past events and efforts had failed.". The past events and efforts were still going on, and came to fruition with the help of the won war... but not because of it.
This is subjective. I guess you could say that Charlemagne's past efforts were still ongoing in their hearts in 1871. At least you admit that your causes needed the war to help them get over the hump.