Hello,

After a lot a reading of org-exp.el and org-html.el I finally figured  
out the
existence of the "HTML_CONTAINER_CLASS" property.

I could then figure a minimal way to make a s5 presentation.
Minimal in the sens of minimum difference with the html exporter.

After setting a few STYLE and OPTIONS lines in an org file,
three steps are needed:
1. Set the HTML_CONTAINER_CLASS to "slide" on level 1 headings
2. Set org-export-html-toplevel-hlevel to "1", so that slide titles  
behave properly
3. Replace in the html output
<div id="content">
by
<div class="layout">
<div id="controls"><!-- DO NOT EDIT --></div>
<div id="currentSlide"><!-- DO NOT EDIT --></div>
<div id="header"></div>
<div id="footer">
<h1>Interactive Python plotting</h1>
</div>
</div>

<div class="presentation">

You need the "ui" directory from the S5 archive to make it work  
indeed, http://meyerweb.com/eric/tools/s5/ .
I attach an example org file and the resulting html (which was  
tweaked according to step 3).

Pierre