I run a small service for Norwegian customers where they get automatically installed and configured Wordpress blogs on their own domains ready immediately after payment is finished. It's quite similar to Page.ly and WPEngine, just aimed at Norwegian customers with Norwegian Wordpress, support, billing etc.
The backend is WHM/CPanel (Apache, PHP, mySQL), with a script running immediately after payment that installs and configures Wordpress and sends the customer an email with their username and password.
Newly registered domains takes some time to propagate though, so for a day or two my customers unfortunately have to use a temporary URL before I can switch them over to their own domains.
Right now my system uses mod_userdir ("serverIP/~cpanelusername"). However, it's not an optimal solution. It looks unprofessional, is confusing, and is quite problematic for both my customers and me.
I'd rather prefer the temporary URL for their blogs to be "theirdomainwithoutextension.host.no", with "host.no" being a domain I own and served from the same server as the customer sites.
I can easily modify the script to create the subdomains on my "host.no"-domain, but how can I seamlessly map the subdomains to folders owned/ran on/by different CPanel/Apache/PHP users?