A user have pointed out that it would be useful to have the workflow write the output data to multiple locations, for example a web server for quick sharing of the data and also a long term backed up storage. Multiple copies of important data seems like a good thing to support.
At a high level, the change would be to pegasus-plan and the --output-site options. It could be changed to something similar to --sites:
--output-sites site1,site2