I for one welcome any efforts to find a POD that end the immediate cry for protectionism in every nation in the early 1930s, but I can't see one, can you? There is a way to stop the European banking collapse, but that is rather smaller...
Yes, the scale of the problem is massive. There is a new book out on the fall of free trade in Britain, which I must pick up at some point. Studying the phenomenon internationally would be fascinating.
The best hope is Anglo-American co-operation - there is quite a lot of researhc on the Baldwin government's good relations with the US, building on this might be the best shot.
Of course expecting Stanley Baldwin and Herbert Hoover to save the world between them somehow doesn't quite ring true.