Modify schema created by Messsage Schema Builder?

Does anybody know how to change the IB Message schemas that are created by PeopleTools for rowset based messages? ( PeopleTools -> Integration Broker -> Service Utilities -> Message Schema Builder ) 

Specifically, the schema that gets built always has the date fields as mandatory.  We want to change the schema to make date fields/elements optional.   If a date value is deleted, it is correct in XML messages as blank, but this breaks PeopleTools' own schema validation.

It is a matter of customizing the (not so straight forward) PeopleCode that builds the schema?  Is there a better way?  Really surprised this is not a issue for others.