In Service Desk 7.7.3 and earlier 'Value Type' on Attachment Attributes are not available on any automatic action.
In 7.8 Value Type can be used on Attachment Attribute on an automatic Reminder in the process.
If you are on 7.8, then you should be able to add an automatic "Add Reminder" in your Request Process and then set up a Value Type to point to your Incident Collection - Incident - Attachment attribute.
You wouldn't be able to get the attachment over to anything but a reminder.
If you want this feature to be more enhanced then I would suggest adding a suggestion on this on our ER Portal: https://community.landesk.com/support/community/enhancementrequests
Kind Regards,
Jenny
LANDESK Support