Kevin,
You should be able to export the XSLFO from Styler to a .xsl file. You should then be able to do an XSLT publish using that stylesheet to generate the raw FO markup.
The generated XSLT should be perfectly legal, but I do think it might be XSL 2.0, so if you try to run it with an XSLT 1.0 engine (like Xalan, which is what FOP uses by default), it might not work. Arbortext's default XSLT processor is Saxon, which supports XSLT 2.0.
Chris