[galaxy-dev] Workflow improvement suggestion

We are finding galaxy really useful but with the implications of users not cleaning up after themselves when running long workflow is hitting on our storage. This could be easily fixed by allowing users to mark steps in a workflow as "KEPT" or "DELETED". Then whenever the workflow is run the files that are just created in passing to the next step and aren't required as output can be automatically marked as deleted and cleaned up as part of normal cleanup operations. Would you consider implementing this, or if not - which modules would be best to look at if we want to do it ourselves? Cheers Dennis