[docbook-apps] Considering XSL-FO as a graphics file format

Hi,

I am working on a DocBook project that has several literal layouts.  They
are listing of XML documents.  To make them easier to read, I wanted them to
be multi-colored; so I wrote an XSL stylesheet to transform them into -fo
with the appropriate inlines to control the color.  I include placeholders
within the DocBook to indicate where the listings are to be placed.  I
transform the DocBook into -fo and then replace each placeholder with its
colorized -fo listing.  I then process the resulting file using XEP creating
a pdf.  This process works fine but it is time consuming and must be
repeated very time there is a change to the DocBook file.

My question is "Is it possible to treat these -fo files as graphics files,
similar to SVG files?"

Gordon Ney