Not just for Resellers, but people professionally needing to add lotsa domains for marketing campaigns, too. We're talking two different things here.
You can already script creation of domains--everything in the Virtualmin UI is scriptable. To create a domain:
/usr/sbin/virtualmin create-domain --domain example.com --pass password
And, of course, all options are also available. Extensive documentation is available for the command line tools here:
http://www.virtualmin.com/documentation/id,command_line_api/What David is wishing for is a Red Hat kickstart configuration file, which with the proper setup (including a tftp server, DHCPd, and a netboot configuration) allows someone to rapidly install many identical machines with an identical software stack. Unless you've got a dozen identical servers (or a few hundred or a few thousand) that need an identical OS and Virtualmin installation, then you don't want the hassle of setting up the kickstart environment. ;-)