To get the ball rolling,
-Poland should not have a coastline; this should belong to East Prussia.
-Bulgaria should have an Aegean Sea coastline
-St. Petersburg should be reflected as a capital and a spawn site.
-Hungary might also count as a capital territory. Some would argue with this, but the economic loss of IPCs and the political damage from its loss basically cause Austria-Hungary to crumble. It was an empire held together with baling wire. The PTR add an interesting element of economic and political collapse. A-H should be the weak political link in the CPs, just as Russia is for the Allies. And I say this as a great lover of playing the A-H empire.
-Maybe raise Bulgaria and Romania an IPC. The addition of Bulgarian resources (reluctantly given) and Romanian plunder (taken without asking) really helped Germany prosecute its war effort at a time when the blockade was starting to put the hurt on it.