We are currently resellers for the sitebuilder by ezot.com. We are looking to bring a similar software package or bette on to our own servers as the revenue share has increased too much affecting profitability.
Please take a look at their site builder. The ability to customize templates, headers, etc are paramount. We also want an admin interface that allows us to uploade new templates, monitor trials, set trial periods, built in affiliate tracking, etc. In addition, we would want to implement domain reseller within the interface like enom or something similar.