Currently there is no easy way to do this. It would require that the system admin acting as the end user to deleting some files. There is no API to support this operation.
Of course it’s possible to change the code in seafevents (Pro only) to delete the files with specific extensions. But it requires deeper understanding to the code.
The only easy workaround I can think of now is to send an email notification to users.
In the upcoming 7.0 version, the seafevents module is redesigned to output file level update events. Based on that we may be able to provide some form of “workflow engine” in the background. Admins can register their own hook scripts for update events.