How to programatically change file user owner
I don't know of a module built to handle this, but you could build something easily enough to do it:


the DB table file_managed handles files, and includes a uid field which is the user ID of the file 'owner'


This could be modified in a custom module, but a MAJOR WARNING that I don't know what potential damage this could cause to other elements of the site, perhaps someone with more experience with the DB could add some advice in this regard