I try to implement a scale when it comes to Russia and the US.  Russia whenever it takes occupied nations back from the Germans can either add it to her territory and recieve IPs for it or she can liberate it without gaining any IPs.  The more territories she takes for her own the closer she goes to war with the US and Britian.  Eventually aid is suspended and after a while war is declared.  After that my friends and I have many rules about what happens afterward.  Also the scale to which these consequences occur varies, but it works.