This could be done using the checkboxes for removal/seen-tagging by just adding an option to edit some fileatributes (namely storage and source or some more eg. seen-tag) for all checked files at once.
is this feature request handled now?
it might still be a hassle to change the source/storage info of a bunch of files but you can now at least automate that to a certain point by copying the ed2k links of the files you want to change into the mass update/change page @ mylist.