Including contentonly module in a structure, render content sections as chapters?

[Peter Desjardins <peter.desjardins.us@gmail.com>]

Hi! I'm trying to write a DocBook 5.1 topic that I can include in a
very large structure and that I can also publish as a smaller
standalone book.

The topic has nested section elements. To create my standalone book, I
want to include the topic module as the only content in the structure
and promote the topic's top-level sections to chapter elements in the
book.

Here's the structure I'm using:

<structure xml:id="myStandaloneGuide">
  <merge>
    <title>My Standalone Guide</title>
  </merge>

  <module contentonly="true" omittitles="true"
          resourceref="myTopicResourceId"/>
</structure>

This results in a book with my title and the child sections of the
topic, which is almost what I need. The book is not valid because the
sections are not promoted to chapter elements.

Is there any way to include the contents of a topic and promote those
content to book-level elements?

I think I can work around this by creating resources for each of the
child sections and rendering them as chapters individually. I'd like
to confirm that there isn't a feature I'm missing though.

Thanks for your help!

Peter