How to remove a digital signature in a web-based form

[StefanS]

When a digitally signed web-based form is rejected and send back the
applicant, the signature must be removed to let the fields fill out again.
How can I remove the Signature node in between the <my:signature2> group?
Ideas:
1. Via managed code upon submitting the form
2. By SPD Custom Workflow Activitie: Set InfoPath field inner xml

Does anyone have a solid solution? Thanx!