Hmm. The problem with peace terms of the form "Change your internal organisation thus-and-so" is that they're hard to enforce. Consider what happens if Germany agrees - perhaps even sincerely! - to write a new Constitution in 18 months, and then when the time is up they produce something almost identical to the old one. Roosevelt is out of office, nobody in Europe has the stomach for renewed war, and the German Army has recovered its fighting strength. This is exactly the reason why the Entente powers retained the blockade in our 1918: Since they were not occupying any German territory, that was their leverage on the writers of the Weimar constitution. Which was therefore written very quickly as these things go.
Now, you don't have that problem: You can keep American boots and bayonets in Berlin until the Germans produce a constitution that pleases you. Or can you? Once the war is over the voters will want to bring the boys home. A large-scale, long-term occupation will, at any rate, be quite unpopular; Roosevelt can probably make it stick, but what of his successor?
I note that between, roughly speaking, 1648 and 1914, peace treaties tended to speak of tangible, enforceable gains: Fortresses dismantled, borders moved, ships and gold delivered. That was also the period in which "pacta sunt servanda" was best observed. (Conversely, when treaties often mentioned "Convert to form X of Christianity", there were 150 years of dreadful attritional warfare.) There were some exceptions to the general rule, such as when Britain in 1713 got the right to deliver slaves to the Spanish colonies; notice that this is an intangible good, and disputes over its enforcement were the main cause of the War of Jenkin's Ear - the whimsical name notwithstanding.
I would suggest that, at a minimum, any internal-reorganisation treaty must be backed up by, in effect, hostages; perhaps an occupation of the Saar, the North Sea ports, and possibly even the Ruhr and the ruins of Berlin.
On the other side, the Germans might try the ploy of offering that the Kaiser abdicate in favour of his son or brother; thus there is symbolic punishment of the man who started the war, but they retain the institution of the Emperor with his full powers. It is of course quite unclear that this would be acceptable to the Concordat, or to Wilhelm; at any rate it was tried without success in OTL.
There's also the question of Austria. In OTL it was a creaky old thing held together mainly by the personal prestige of Franz Josef; if your Austria is similar, then the actual demands of the Concordat powers may be rather secondary to its internal dynamics. Greater Serbia, Greater Bulgaria, Pan-Slavic Union? This last of course would likely raise some alarm in London, and secondarily in Paris. Even Poland, perhaps, is not yet dead, although it may have more trouble enforcing its independence against an at least nominally victorious Imperial Russia than it did against the exhausted Red Army - and even that was a close-run thing.
Incidentally, Schleswig should be returned to Denmark. Holstein only if the Concordat feels short-sightedly vengeful.
Now, you don't have that problem: You can keep American boots and bayonets in Berlin until the Germans produce a constitution that pleases you. Or can you? Once the war is over the voters will want to bring the boys home. A large-scale, long-term occupation will, at any rate, be quite unpopular; Roosevelt can probably make it stick, but what of his successor?
I note that between, roughly speaking, 1648 and 1914, peace treaties tended to speak of tangible, enforceable gains: Fortresses dismantled, borders moved, ships and gold delivered. That was also the period in which "pacta sunt servanda" was best observed. (Conversely, when treaties often mentioned "Convert to form X of Christianity", there were 150 years of dreadful attritional warfare.) There were some exceptions to the general rule, such as when Britain in 1713 got the right to deliver slaves to the Spanish colonies; notice that this is an intangible good, and disputes over its enforcement were the main cause of the War of Jenkin's Ear - the whimsical name notwithstanding.
I would suggest that, at a minimum, any internal-reorganisation treaty must be backed up by, in effect, hostages; perhaps an occupation of the Saar, the North Sea ports, and possibly even the Ruhr and the ruins of Berlin.
On the other side, the Germans might try the ploy of offering that the Kaiser abdicate in favour of his son or brother; thus there is symbolic punishment of the man who started the war, but they retain the institution of the Emperor with his full powers. It is of course quite unclear that this would be acceptable to the Concordat, or to Wilhelm; at any rate it was tried without success in OTL.
There's also the question of Austria. In OTL it was a creaky old thing held together mainly by the personal prestige of Franz Josef; if your Austria is similar, then the actual demands of the Concordat powers may be rather secondary to its internal dynamics. Greater Serbia, Greater Bulgaria, Pan-Slavic Union? This last of course would likely raise some alarm in London, and secondarily in Paris. Even Poland, perhaps, is not yet dead, although it may have more trouble enforcing its independence against an at least nominally victorious Imperial Russia than it did against the exhausted Red Army - and even that was a close-run thing.
Incidentally, Schleswig should be returned to Denmark. Holstein only if the Concordat feels short-sightedly vengeful.