Could the West provide Ukraine is a bunch of shipping vessels that they then use to make a surprise landing with several divisions of special forces, trained to live off the land, in the Far East?
It seems like Russia would be totally unprepared for this. They could probably advance halfway down the Siberian Railroad and just hold there, cutting them off from their main revenue sources.
It would also probably kick off independence movements.
After months, when Russia finally gets it shit together, they might have indigenous allies, or barring that, they can blow all the gas rigs on the way out.