1. A front-end multiple php versions switcher on the display page instead .htaccess for each clients.
2. Smarty is a free and opensource php template engine. I think it is very flexible. *.tpl is the extension for smarty files. However it is hard to create skins of Kloxo-MR. So I think you can use it:
http://www.smarty.net/.
Thanks for your great work