Dynamic Signatures

Have you considered using different fields to represent the evangelist's contact information for your leads? You would be able to use tokens for the signatures.

Where would I create these fields? The field would have all the info or the token would contain all the fields? I would like to have a token on each email and when I update this 1 token, the info changes anywhere that token is placed. Im fearful that I may still need to go in and change the token across all the emails. 

If a huge chunk of your database is split between 20 evangelists, and you know that the evangelist program is going to be a long-term initiative, you could create fields on the lead records. They'd be similar to the Lead Owner fields, where you have to update the lead information and you can use tokens to display the correct evangelist per territory.

You could also use Segmentation for this too; group leads by territory and place them in different segmentations so you can use signature snippets in your emails. Then you'd only update one email instead of 20 :)

Have you considered using tokens to represent who it is coming from and their signature?  On most of our outbound emails, we have used tokens at the program level and can quickly swap these out once vs. going into each email within the campaign or track and updating each individually.

http://community.marketo.com/MarketoTutorial?id=kA250000000KysJCAS

HTH