Actually you might as well kick Sibirs butt, since you have a CB & it lies in ROTW (0 BB for DOW and taking provinces).
You can even attack the lonely capital of Sibir every 5 years for a nice 100-200 D addition to your treasury =).
You can even attack the lonely capital of Sibir every 5 years for a nice 100-200 D addition to your treasury =).