If there were an Event  prior to ContentPostRender (before template is fetched
by Smarty) we could have an elegant template switcher (not just Stylesheets, but
whole template)! :) See dirty UDT solution here
http://forum.cmsmadesimple.org/viewtopic.php?f=4&t=19028&p=241444#p241444
I would write a module that handles template array and add a nice jquery bar at
the top where templates can be selected. It could be also use it on
themes.cmsmadesimple.org so that templates can be previewed prior to
downloading.