Does the “Deploy this update via NFS mount” action work for you?
If not, you could make a copy of the fixlet and modify one of the actions to use a specified path.
Another option would precache it using the “start client downloads before the constraints are satisfied”. The issue you might have here is that the updates could be rather large and you would need to look at the _BESClient_Download_PreCacheStageDiskLimitMB. Looking at the SP 7100-05-03, it is 9.76GB.