The WFA provided "reverse resync snapmirror relationship" workflow looks to do all the work of setting up the new snapmirror from old-dest to old-source. It takes a broken off snapmirror as the input.
I was trying to create a workflow using this to perform the snapmirror break and then go right in to the reverse resync.
In researching this further, I am thinking that I have to create a reservation in the "snapmirror break" step that will update the cache to show the snapmirror is now in the "broken_off" state. Does anyone know if this is correct? and if so, where to find an example of how to update the cm_storage.snapmirror entry to be "broken_off"?