I put together a rule to do this during our POC and initial test deployment.
In MEG7, add a policy to the smtp protocol for email is outbound, inherit from default, disable sender auth (spam column), create a custom content handling policy (in the policy options column). Under Content Handling Settings, Email Options, Basic options, check mark "Enable the use of disclaimers." I did it with html and plain text. Place "after any message text". And give it a whirl.