the "other way" doesn't sound badly!
it would be nice if somebody could make a shader that displays everything in white and only the objects which should get a shadow are displayed in black! Than, you render the view to a cubemap and display it with the projection shader! The only problem is the backside projection! I don't know how to remove that effect. Maybe somebody like "ello" could do this job for us, I would pay anyone who could make it!
cu chris