Require Attachment in Ticket

Require Attachment in Ticket

Hi:

We have certain requests that we require an attachment.
We have a web form which includes an Attachment field, however that is the only field that we can't mark as Required. 

Since the GUI/WYSIWYG doesn't have the required checkbox, I thought of an Automation: Upon ticket create, if an attachment isn't found, set to status to Waiting on Customer, and adjust the SLA accordingly.

However, I looked in the Workflows, Blueprints, and there doesn't appear to be any way to check for attachments.  Is there a way to do this?  Obvious the easiest way would be to just require it on the web form.

Thanks