I know there are probably quite a few "WI Germany won WWI" threads, but here's my take on it. I won't be able to put it as well as you all, as I've no experience at creating timelines and so on, but here's my crack at it. Let me know what you think, what's most and least plausible, any additions to this timeline and what the consequences would be if this "WI" happened:
Germany wins World War One. Their plans for north-eastern Europe come to fruition as the Kingdoms of Finland, of Lithuania and of Poland, the United Baltic Duchy and the Ukrainian Kossack State are all part of the post-war settlement, all of which are German satellite states. The German Empire, still in tact, and in fact enlarged by acquired Africa and Caribbean colonies from France and Britain, now operates a system with these new states whereby Germany will exchange funding and support for the resources of these new nations.
The United States, which ultimately struggled to decide on whether to remain neutral, as the isolationists wanted, or to side with Britain, as the internationalists wanted, ended up remaining neutral, to the bloody end when Britain and France surrendered and signed an armistice with Germany. Though Germany had won the war, it was still hit hard by the economic costs, so when the United States demanded to be part of the peace negotiations, Germany felt obliged to accept the demands of its inevitable future trading partner. The United States' change of policy to intervene had occured when the fate of the Entente powers was sealed, ever since Germany was in a position to concentrate all her forces on the Western Front since Russia signed a separate armistice. Woodrow Wilson, who had by now clearly shown sympathies towards Britain, proclaimed to the American people, weeks before the armistice was agreed, that their complacency had allowed dictatorship to swallow Europe, and democracy would be dead and buried there unless they supported the democracies of France and Britain. Another major concern of the United States was that, whilst they had had very good relations with the main colonial power, Britain, they felt that if Germany replaced Britain, conflict between Germany and the US would be inevitable, due to their contrasting views on government rule and foreign policy. Also, though to a lesser extent, the US felt uneasy about the presence of communism in Russia, the world's largest country, and wished to nip it in the bid before it stabelised and spread. Either way, a Europe dominated by an aggressive Germany or a communist Russia was going to cause the US problems somewhere along the line, hence their insistence on involvement in the peace process.
Germany and the United States played the largest roles in the post-war settlement, after the Austro-Hungarian Empire and the Ottoman Empires had already broken up by this point. Germany maintained its current borders, except the inclusion of Austria as a new German state. When the Austro-Hungarian Empire fell, the Austrian government could see that the areas of greatest wealth would now be out of their grasp, making them very vulnerable economically. Therefore, the best answer to the Austrians seemed to be to unite with Germany, as they would have been many years ago, were it not for Austria's land empire at the time. At Germany's insistence, the aforementioned monarchies were created, with German royals placed on the thrones (except the Ukrainian Kossack State, where Pavlo Skoropadsky was maintained, which also acquired Bessarabia at the expense of Romania). The Austrian Emperor, Charles I, was placed on the Hungarian throne instead as King of Hungary, whilst Bulgaria's contribution to the war was rewarded by their acquisition of Macedonia. At Wilson's insistence on self-determination, the republic of Czechoslovakia and the kingdom of Yugoslavia were created, as per the wishes of the peoples of these countries.
Also, with regards to Russia, which both Germany and the United States distrusted, the two promised to return Cyril Vladimirovich, pretender to the Russian throne, as a restored Tsar of Russia. However, the new Tsar, at American instruction, would have to make large democratic concessions, reducing his role to a constitutional monarch. If he accepted this settlement, he would receive aid from the United States to restore stability to Russia. Meanwhile, at the threat of combined United States and German forces, along with White Russian forces already in existence, Lenin withdrew to Belarussia, and promised to confine his communist government there alone in the peace settlement.
Once this settlement had been agreed and signed, Europe already seemed to divide into German and non-German affiliated states, with Britain, Ireland (which had gained independence after defeat), France, the Benelux states, Italy, Albania, Greece, Yugoslavia, Czechoslovakia and restored Russia all uneasy and fearful of German influence, Czechoslovakia in particular as it was surrounded by German-affiliated states. But whilst Albania, which was initially hostile to the other European powers for their old interventionist policies, soon seeked stronger ties, Yugoslavia drifted away. Although Yugoslavia had been aligned with the United States, conflicts within Yugoslavia between the different ethnic groups, and the government's harsh response, meant that Yugoslavia began to conflict with the US and allied states, pushing the Yugoslavs closer to the Germanic states.
Meanwhile, Spain and Portugal were unstable republics that were left by the rest of Europe to decide their own problems, along with Romania, which was also suffering instability. The Scandinavian states and Switzerland remained neutral.