Switching signatures using an agent?

A user has asked if there is a better way to change his signature. He has 2 signatures for different roles that he has to use with approximately equal regularity.

Could anyone help me with creating an agent or something that will allow him to switch signatures with a button press or two?

I was thinking a button on the action bar, that when clicked would drop down a list or display a dialogue with signature1, signature2 as options for him to click on, then would assign the chosen signature to the memo.