The suexec-docroot is currently hardcoded to /var/www during compilation, which makes sense for "simple" webserver. As soon as users are having virtualhosts in their homedirs, suexec cannot be installed for these users, as /home/user/www.example.com is outside of the docroot. Our current fix is to recompile the httpd packages with a changed docroot. It works, but is a nuisance. It might make a nice addition to RHEL to be able to make the suexec-docroot configurable by either editing a /etc/sysconfig file or by adding a configure tag to the main httpd.conf.
Thanks for contacting us. It's really not safe to start having the suexec binary start reading files to determine the configuration; it is a standalone binary for a good reason. You could place the user-managed vhost directories in /var/www/<vhost> instead, as is normal practice.