Do you think that the west might have been happy to sell oil, ammunition, and other supplies to the Germans? I don't really think they would have supported the USSR because if they were neutral then they wouldn't have to risk their own ships to sell to Germany while supporting the USSR would have still required bypassing Uboats which might not be worth the profit to loss of life
Whilst I doubt there would have been any tears for Stalin, I don't think either the French or the British would have been willing to allow a huge German empire to have been created by conquests in the east. (Nor, taking the longer term view, would it be in their interests to see Germany destroyed and the Russians adjacent to western europe)

The only issue might have been, if 1940 went as well as 1941, whether the speed and scale of German (apparent) success would have been so great that the UK and France would have held back from declaring war. After all, Russia had collapsed in a war with Germany once before. As the UK and France did in fact declare war over Poland, when it was obvious that Poland could not resist the German invasion, I can't imagine they would have held back from declaring war over an invasion of Russia in 1940 even if that invasion was going very well for the Germans.