is it possible to have a mass change to FormID?
You can multiselect any number of records, then R-Click > Change FormID and you'll be met by a "Choose target" prompt. You can then change the FormID's en masse that their first two characters will be that of the target plugin which must be in the plugin's masterlist. References to these forms will also be automatically updated. After doing this, all the selected forms will be *
injected into the target just as the preorder packs introduce their content.
*
Injecting new forms into FalloutNV.ESM, for modders, is probably not a good idea as A) the ESM is bound to change again and B
) modders' 00 FormID's would invariably end up clashing. By the same token, if you inject forms into a mod that gets updated, your forms might clash with new ones added by the author(s). To avoid that, one could change the NOID in the target to offset the renumbering of the injected forms, but there's usually just no reason to have forms injecting all over the place unless temporarily pre-merge.