I wrote a brief scenario about a Protestant victory a few years ago. It's about as comprehensive as I could imagine a Protestant triumph (half-way) realistically getting. It's based around a map portraying the aftermath in the somewhat longer term.
The map we see above portrays Europe in the year 1725, but the origins of this tableau go back a century, to the Twenty-Five Years' War, which is also called the War of German Liberation. The Protestant cause prevailed, aided by the (nakedly opportunistic) support of France. As it happened, Gustavus Adolphus of Sweden and Frederick V of the Palatinate both managed to avoid an early death. The successes that their side achieved led Gustavus Adolphus to lend public support to Frederick V's claims: an event that soon cascaded into the formation of the Second Protestant League— once again with Frederick at its head.
The war concluded in 1643, with the capitulation of the House of Habsburg. The last hope of the Imperial side had been an attempt to induce Denmark to switch sides. This, however, was discovered before Denmark could act, and only prompted Sweden to mount an aggressive and ultimately triumphant campaign against the Danish positions.
The defeat of the Habsburgs entailed nothing less than the complete abolition of the Holy Roman Empire. Ferdinand III had to endure the humiliation of not only renouncing his own Imperial title, but of formally recognising the newly-crowned German Emperor: none other than the head of the Protestant League, Ferdinand V himself. (As was famously noted at the time: "
King in the cruel Bohemian Winter, but Emperor come splendid German Summer.") It was not that Frederick was somehow an ideal candidate. It was more that the other contenders (Gustavus Adolphus of Sweden and Johann Georg of Saxony) proved too divisive, whereas Frederick was acceptable to almost everyone.
It helped that the Second Protestant League was far broader than the first had been, which lent a lot of credibility to Frederick as a reasonable and sufficiently legitimate candidate. Thus, the scorned King became the hailed Emperor— albeit a rather powerless one, who was in practice just the
primus inter pares of the Protestant German monarchs. (This, in fact, was another reason why Frederick became the candidate for the position: the fact that he was more or less a mediocrity made him sufficiently unthreatening to the other monarchs.)
Still, an Emperor is an Emperor. In humiliated Austria,
former Emperor Ferdinand III would now be the one to console himself with the 'mere' title of King— which he at least retained for longer than a single winter. To add further insult to the injuries of the degraded Habsburgs, the Ottomans laid claim to all Hungary, where Protestant rebels soon turned into willing vassals of the Turkish overlords, so long as they were allowed to govern themselves. (Or at least: they were willing to be vassals for the time being...)
The newly-founded German Empire deliberately excluded the deeply Catholic regions in the South, but incorporated Silesia, Bohemia-Moravia, and a wedge cutting South all the way to include the Protestant regions of Württemberg. Bavaria soon moved to bring the remaining lesser Catholic statelets under its own aegis, which was tolerated in order to definitively keep them out of Habsburg hands. Poland-Lithuania, meanwhile, was harshly punished for its support of the Catholic cause: the German Empire annexed the coastal regions of Poland, which the Germans desired in order to establish a direct land connection to East Prussia.
France certainly demanded a high price for its crucial support: excluding only the overwhelmingly Protestant regions on the Left bank of the Rhine, France annexed all the formerly German regions to the West of the Rhine. The former Habsburg Netherlands were additionally divided between the Dutch Republic and France. The lion's share of these spoils went to France, although the Dutch gained Gent, Antwerp and Brussels. In any event, the Dutch were further rewarded with certain gains on their Eastern border— most notably Kleve and Bentheim.
Switzerland underwent some border adjustments, and swung firmly into the Protestant camp. The Germans actually wanted to absorb Switzerland directly, but Bavaria had established that pesky corridor (inhabited by staunch Catholics) right in between Switzerland and Germany. Of course, there was also the matter that France didn't want Germany to get
too powerful. Especially since Sweden had opted to resolve its differences with Denmark separately, resulting in a war that Sweden looked set to win. France knew all too well that a powerful combination of Protestant states would eventually become a threat to.... France. Thus, having opportunistically gained what it wanted, France quickly began to mend fences with the Catholic states.
Sweden indeed defeated Denmark soundly, and demanded the permanent cession of Scania, Halland, Blekinge, Bohuslän, Trøndelag and Bornholm (in addition to a substantial indemnity).
A period of minor wars and diplomatic struggles began. Britain saw its monarchy restored. The fact that France had greatly extended its power, only to then turn back to the Catholic camp, soured even Charles II on the prospect of a French alliance. Instead, with its former ally Denmark humbled, England would seek a naval alliance with the Dutch Republic. This was motivated in no small part by a desire by both countries to guard themselves against future French aggression.
James, the Duke of York, was greatly at odds with his brother's policies. Their younger brother Henry, the Duke of Gloucester, was instead a great proponent of the Dutch alliance. He was sent to the Netherlands to argue for a treaty as soon as Charles II took the throne. Not only did he succeed, he returned to England with an engagement on the horizon. While in the Netherlands, Henry had met Maria of Orange-Nassau, sister of the late Stadtholder Willem II. The two found that they were an excellent match, and a year later, they were wedded. A year after that, their son William Charles was born. Ultimately, this would cause the childless Charles II to agree to the exclusionary measures that Parliament proposed to keep his Catholic brother James off the throne. Instead, the firmly Protestant Henry would be his heir.
Unwilling to fight England and the Netherlands at the same time, especially not with its own flank exposed to Protestant Germany, France abandoned any plans of waging further wars of territorial expansion against the Dutch Republic. Instead, the French policy became centred exclusively on building up a new Catholic alliance. One that would see France—now clearly the pre-eminent Catholic power—placed at its head. France successfully supported Savoyard ambitions, cultivating a staunch ally in North-Western Italy. Not to be outdone, Venice sought to exploit Habsburg weakness by annexing certain border regions, but this proved to be far trickier. Ultimately, Venice had to sell its Illyrian possessions to the Ottomans in order to finance its own war with the Austrians. On the plus side, Venice did manage to wrangle certain territorial gains from that campaign.
The Ottomans, meanwhile, were faced with the unpleasant consequences of their victory in Hungary. The new Protestant rulers of the country soon grew tired of being vassals. They claimed all of Hungary, including the regions governed directly by the Ottomans, and made a bid for independence. A successful, German-backed bid. This in turn allowed France to lure the irate Ottomans into the ranks of the anti-Protestant alliance. Furthermore, French influence, the enormous weakening of the Ottomans and the threat presented by Germany ensured the election of François Louis, the Prince of Conti, as King of Poland in 1697.
Come 1700, two major issues presented themselves: the Spanish Succession, and the Russian desire to finally gain proper access to the Baltic. Although France and Austria both had a claim to the Spanish inheritance, both knew that fighting over it would only serve their enemies. Instead, they resolved the matter diplomatically: France would press its claim to the Crown of Castille, while Austria gained the Crown of Aragon. The former would go to a separate line of the House of Bourbon, while the latter would go into full personal union with Austria under the Habsburgs.
The Russian Baltic issue was resolved through war, but not one against Sweden (which many had expected). The fact that France had enticed the Ottoman Empire into its alliance had soon brought Russia into closer league with the Protestant bloc. Rather than fight each other, Sweden and Russia worked together in dismantling Poland-Lithuania. As it happened, the Swedes did most of this, while the Russian simultaneously pursued an offensive against the Ottomans. The Germans, Dutch, English and Hungarians ensured that France and the other Catholic powers could not intervene, by declaring their resolve to enter the war if such intervention was undertaken.
By 1717, Poland had been reduced to a rump state, while Russia had driven the Ottomans from the Northern shores of the Black Sea. Sweden had conquered the vast Polish-Lithuanian territories, including those that could provide Russia with access to the Baltic. Having little use for such an inland empire, and knowing how much Russia needed those territories, Sweden swapped them for Karelia and an Ingrian border adjustment. A Danish attempt to re-take Scania provided Sweden with the perfect pretext for a subsequent anti-Danish war. In this, Sweden colluded with Germany and Britain. Together, these powers moved to disassemble what remained of Denmark's empire. Sweden took the lion's share, but although German gains at Denmark's expense were modest indeed, Sweden agreed to cede its own lands within the German Empire in exchange for German support. Britain, for its part, lent its navy to the undertaking, and received Iceland, Greenland, the Faroes and Jan Mayen.
France used the fact that its enemies were distracted to set certain affairs of its own in order, lending military support to the House of Savoy and thus uniting North-Western Italy under an allied regime.
It is now 1725. The Protestant and Catholic blocs (with their respective Orthodox and Muslim allies in Russia and the Ottoman Empire) have now both settled all their outstanding issues. They are both firmly aligned against each other. An all-encompassing war has been avoided thus far, but an intolerable pressure has by now built up. A grand conflagration is not far off, and everybody knows it. "
All Europe is now on the brink of war," a philosopher in the Dutch Republic notes in his writing. "
The moderate seasons have come to an end. No mild Spring, no gentle Autumn. This is the fierce age of extremes; of burning Summer and icy Winter."