Yes, prevent the crazed Plan XVII from replacing Plan XVI and improve France's performance in the West. Hopefully the Western Front would be further north and more in Belgium rather than France - that would have spared the Entente from launching numerous costly offensives and instead forced the Germans to do so otherwise.
Meanwhile, keep Russian performance as bad as IOTL, but don't let them do the OTL Kerensky Offensive.
Disagree. Marching into Germany would have killed off the "stab in the back" myth. IOTL much of the German populace did not even believe that they were losing - until Hidenburg surrendered.
Next, actually occupying Germany means that you can enforce your intended restrictions and reforms (e.g. land reforms targeting the Junkers), purging various reationary elements from the Court, the Civil Service and the Army Officers, or suppressing paramilitary groups like Freikorps.
I quite agree, except for the fact that it wasn't Hindenburg who surrendered. He and Ludendorff just sneaked out the back door and let civilians do the surrendering.
But, yes: Actually occupying Germany would have helped a lot in removing many heavy legacies which hung around Weimar's neck. Like
@AltoRegnant already said.
And if Russia is on the path to democracy instead of communism in 1918/19, this becomes more likely, too, as the Western powers don't have to fear to lose too much energy in occupying and weakening a potential bulwark against Bolshevism, and instead would have encouragement and potentially participation from Russia in the endeavour of occupying Germany.
But how do you get the Entente to actually go for "unconditional surrender" - or else prevent Germany from throwing the towel?
And how do you keep Russia from turning Red? Preventing the Kerensky Offensive goes some way, but it doesn't solve everything. So let's look into further proposals:
Perhaps succesful Gallipoli. German monarchy would stay around but evolves towards more democratic system. And since Britain would be worried about stronger Russia, it could pressure France to accept not that harsh peace terms for Germany.
For Russia this would mean no revolutions and no rise of Bolsheviks. But there would be now more pressure towards democratic system since millions of soldiers would demand more political rights and other reforms. Tsar just can't sey easily "no".
If Gallipoli had been successful and the Ottomans had sunk into chaos, Bulgaria would in all likelihood not have joined the Central Powers. That would have been good news for Serbia, but other than that, would all this in turn have prevented Romania from entering the war? If not, then Romania's entry on the Entente side would have triggered Bulgaria's entry on the CP side, only later, and the A-H campaign against Romania would have gone similarly to OTL, creating a not so different situation in Central Eastern Europe, except that the Ottomans are finished off early on, Venizelists probably join early in an opportunistic bone-picking, so that Bulgaria's victory over Serbia isn't 100 % certain yet, especially if Britain and France can send more aid because the Ottomans are collapsing anyway or already out of the war.
If Romania stays out of the war, though, which might well happen, or at least doesn't join until very late when Entente victory becomes absolutely certain and Bulgaria isn't a threat, then, on the one hand, Russia's front lines are considerably shorter (especially if the Ottomans surrender). On the other hand, Austria-Hungary's frontlines are A LOT shorter and it's by far not as overstretched as IOTL.
Let's go with the latter option because it's more interesting.
For that matter, let's say the Dardanelles straits are forced and Istanbul is threatened right away in March 1915. The Ottomans would probably not surrender right away, but evacuate their government. Let's say this is the moment when Venizelos succeeds in joining the war on the Entente side, and a disheartened King Constantine can't muster the strength in him to push him aside and prevent him from doing so. No National Schism in Greece, thus. Instead, Istanbul is threatened from all sides now, and ultimately falls, allowing Britain and France to ship support through to the Russians. The horrible performance of the CUP leadership in the war might be sufficient for their opponents and opportunistic forces to push them aside, which would help stopping the Armenian genocide - another good thing. At some point in the second half of 1915, the Ottomans seek terms and a ceasefire is concluded. (They now have to deal with insurgent Arabs, but those Arabs now don't necessarily have British backing.)
What now? Britain and France can free up quite a lot of forces, they can supply Russia and prop up Serbia. The Italian and the Western Front can also be strengthened.
Russian forces from the Caucasus Front are freed up, too.
But by that point, they have still already lost the Battle of Gorlice-Tarnow, and the Great Retreat has happened, too, for I don't see why it would not have occurred, it is too early for new Russian forces or Anglo-French material support to have arrived on time.
And even with lots of troops and lots of materiel, the Battle of Lake Narach was lost in 1916. Yet more troops and more firepower might not have averted that. Russia had a problem with its military leadership, which would not have been solved by the Ottoman collapse.
So, Germany is overstretched in the East, and Britain and France can bring a lot more resources to the Western Front. OHL should have seen the impossibility of winning the war when their Ottoman ally collapses, but do they really?
I am not a military expert, so I don't know how the war on the Western Front would actually go. Could Britain and France really have broken through and pushed back early on, even without the US in the war?
Let's say they can't. So the war drags on through 1916, Germany and Austria-Hungary, but also Russia begin to look rather hungry, the war has become massively unpopular here. With somewhat better fortune, the series of French mutinies might have been averted, further strengthening the Entente on the Western Front.
Starvation in Petrograd and dissatisfaction with the horrible performance of the elites still causes the February Revolution of 1917 to break out. But around the same time, the British and the French finally manage to break through the Hindenburg Line and start a successful Hundred Days Offensive more than a year ahead of OTL schedule and without US participation. Maybe now Romania joins in opportunistically, but now it's too late for Bulgaria to pick the other side, so they remain neutral. With Entente support, the Romanians stay in Transilvania and that's it. Maybe the A-H collapse begins in Hungary now.
OHL knows they're lost, and like IOTL, they push civilians to the fore to concede it, the sly treacherous cowards that they were. But in the first half of 1917, and without a Russian October to inspire it, there aren't yet any Revolutionäre Obleute networks forming everywhere to organise widespread mutinies and revolts. Also, if a last hooray for the navy is not ordered, Kiel doesn't ignite the powderkeg, either. Thus, it's not a group of republican politicians signing alt-Compiegne. It's probably not Bethmann-Hollweg, either, for he must certainly resign after such a course of events. Is it Michaelis, who succeeded him IOTL, or is it someone with real reformist inclinations?
Whoever it is, he is not faced with a collapsing state order and revolution in the streets. And he can't hope for a lenient Wilsonian treatment, since the US are not in the war. And he doesn't have to fear a Bolshevik revolution because the world doesn't that kind of thing yet. He has to sign alt-Compiegne anyway because the war is lost, but in the light of the incredible unpopularity of it, he might hold off too long, and Anglo-French troops might already have set foot on German soil by that point. (That would be holding it off for quite a while indeed, to be honest. And it would be only the Westernmost edges of German soil anyway.) If he waits that long, and the Entente must fear a potential rebound because the German Army isn't disintegrating, just losing ground, then full occupation to oversee demilitarisation might be a demand of alt-Compiegne. But it may well not be. If it isn't, then we're not necessarily getting the good conditions for German democracy.
Hm.
Anyone else got an idea?