How do I dynamically assign a list of Approvers upon submission?

There are two user defined fields (ACApproversDefaultPre and ACApproversDefaultPost) and if they contain a list of names they will be concatenated with the Approvers List in the Profile Document. The order will be ACApproversDefaultPre + ACApproversList + ACApproversDefaultPost.

The Demo form "XYZ Authorization (Dynamic)" demonstrates how the ACApproversDefaultPre/Post can be used to look up and return a list of Approvers from a view of the XYZ Routing Rules. You can extend this to return the Approvers from wherever you might have them.