I don´t think there is a feature that can help you with this. A restart of the process will terminate all running processes at once. Blocking the Client in MWG won´t help, since the download already started. You could try to block the Client with a Firewall which will prevent him from updating the progress page requests. If MWG notices that the client does no longer check for the status of the download, it will be cancelled after a while.
i such cases you can try to combine bandwidth management, content type und filesize to manage the use of your bandwidth. This is not the solution for an actual problem but can prevent such problems in the future.
Yes, we do have management in place. We also do not allow files bigger than 200MB to be downloaded during business hours.
These rules do not catch everything as it depends on how the web site is coded.