Email signature in mail templates: add current user's name to signature

I want to use the following workaround for email-signatures for email-templates:
I want to create the signature dynamically into every email-template.

This works well - so far - by using the following variables:
and so on.

the contact_user is always that user that is responsible for the contact/company. In our case we are a small team and everyone does everything. So I want that the username of the CURRENT answering / mailing user displayed in the signature.

responsible for contact is Jane Doe
the current e-mail is created and sent by Andrew Lewis

so I want Andrew Lewis and his department displayed, not Jane Doe’s.

Is there a way how to get this done?

Thank you in advance,
bye EP