I wouldn't prohibit it. I mean, a RL Germany that was victorious in WW2 would most likely not try to destabilize the Russian monarchy, because the more democratic systems around, the more questions asked by the own population. But then, maybe Germany hates Russia so much after the war, that they just want to cause trouble for them now and deal with the fallout later? Who knows what has happened in the war!
Btw: The success chances of Lenin should be reduced after the War methinks. Guess its a lot harder to do a revolution with all the monarchist military around.