Not sure how many Topliners or Eloqua customers are aware of but the platform comes with one of the most advanced functionality to utilize Signature Rules. You can find out the details http://topliners.eloqua.com/community/know_it/blog/2012/05/25/signature-rules. It allows you to have campaign emails sent on behalf of several senders based on any criteria that you provide.
Do share how you use it or what results it has produced for your campaigns.
Thank You
Amit Pandya