Okay, so I have been looking over some of the old threads about the possibility of a Franco-German War in 1905, WW1 in 1905, etc. and one of the things that emerges clearly from them, and what I have read about early twentieth-century Germany in general, is the Germans' fear of their dependence on imports and their resultant vulnerability to blockade. This was one of their big motivations for their naval buildup. So my (very rough) idea is that we could get TTL from army-navy institutional rivalry. Perhaps in the very late nineteenth or the first five years of the twentieth century, some incident happens that makes the German high command even more worried about being blockaded, and one or more high-ranking army officers begins pushing for my version of Barbarossa as a simpler and easier approach than the direct naval buildup, particularly given Britain's overwhelming naval preponderance. Perhaps this requires some other than Schlieffen as Chief of Staff, though. Austria would be motivated by the desire to have Russia permanently removed as a real or potential ally to its Balkan enemies. When the Russo-Japanese War and the 1905 Revolution hit, the Germans decide they will never get a better chance than this and strike.
Turning to your specific points, none of the areas I have referenced in my posts are going to be independent post-war. Depending on their degree of economic importance and the extent of resistance, I might consider allowing them some degree of autonomy, though. As I indicated in my reply to CommandoHowiezter, the areas for which I have really big plans are Ukraine and the Caucasus, so Poland might fall into the former category.
As far as the elite being uncomfortable with a Russian revolution, I actually agree in a way, but sooner or later they are going to have to decide whether that is really more uncomfortable than the Czar's armies sitting just across the East Prussian border from their big estates. Besides, revolution in Russia isn't really the end goal for the Germans here. It is a means to the end of a Russian collapse. The end goal is to have what is left of Russia turn into a kind of European equivalent of late Qing and Warlord era China-Multiple, fragmented polities incapable of real unity, which the Germans can play off against each other.