Edit multiple users/files at once

hello there,

here is what i want to achieve:
users (30 - 60) can be grouped and those groups have different access to different files, regarding their group.
file 1 is accessible by group A and B.
file 2 is accessible by group B and C.

how i solved it:
a blueprint for the users, extending their form with a tags-field.
same for files of a page, adding a tags-field.
if a tag from a user matches a tag from the files it is accessible.

so far so good, it works.
now i got ask if i can make the editing of the user -> file relation easier.
for example selecting multiple user and give them all the tag »A«.
or selecting multiple files and give them all the tag »B«.
this is where i stuck.

where would you hook in?
i am not sure if i should alter the backend.
or just make a new page, only accessible by the admin, which has a custom form and use $page / $user ->update() to save the data?
what would you do?

looking forward,
and thanks,

You’d have to do it programmatically via $user->update(), there is no other way to batch edit users.