Well, mostly OTL, if you refer to the Polish-German border changes after the Great War- the minimum loss for Germany would probably be Poznan, and the maximum would probably be their OTL losses minus Danzig. A relatively likely result would probably be that they walk away with a minimalist interpration of the Corridor and all of Silesia.I haven't really put a whole lot of thought into that aspect of the scenario.
What do you think will happen?
I think the sixth iteration of the TL will feature Slovakia going with the Hungarians and the Czechs going with the Germans.
The Czech rebellion can then stab the Germans, not the Hungarians, in the back.
One problem with the Czechs going up against the Germans is that the Germans aren't just placed in convenient border areas- they were also spread in enclaves all over (mostly) Bohemia, which means the Government has an already in-place loyal force that can- and almost certainly will, out of self-defence- act to fight the revolutionaries, and that the Czechs, well, would be comparatively smaller as a minority in Germany than in Hungary. That, of course, means it is less likely to cause really Bad Stuff to happen to Germany, compared to what your version here does to Hungary.
One idea might be to scrap the Great Czech Revolt, as such, and replace it with a Great Slav Uprising- the Czechs, Slovaks, Ruthenes, Croatians and Slovenes all rising up, co-operating to strike against Germany and Hungary. That'd be bad news for Germany. Or just have the Slovaks, Croats and Ruthenes fill the role of the Czechs, if you want to limit it to Hungary (and want to let Germany keep Slovenia- a bad side might be that it might force you to keep Czechia in Germany, as well). Either way, an independent Slovakia is most likely in the cards. Croatia already seems to have gotten independence at some point- I guess after Hungary sued for peace- so for them, not so much change, I guess- although their national pride might be more with a more active part in bringing down the Hungarian oppressor!