I think there's an element of truth to what you say but I don't know if it would work. Russia will presumably still want to export its' raw materials and grains

I think there's an element of truth to what you say but I don't know if it would work. Russia will presumably still want to export its' raw materials and grains, even if not directly to the West. Because trade is very much global, countries will re export Russian imports to the rest of the world. This is actually how Russia's economy worked during the Soviet era with a surprising amount of indirect trade going on between the USSR and the west. While the sanctions are likely to be punishing for both sides with China especially willing to act as a middle man I suspect the actual effect of sanctions on Russia / west End to end trade will be less than expected and will help further strengthen China's position. And from a purely international realist position, western governments have never given a damn about people in the third or developing world starving and I can't see that changing now.