We're happy to announce that this will be possible with Version 7.0. Introduced in our latest beta build. The System URL and System SSL URL fields have been combined in WHMCS 7.0 to a single field. It is recommended that an SSL enabled URL be provided for the System URL at all times. When SSL is available, it will now be used for all requests, both admin and client side. If a System SSL URL was defined prior to upgrade, this value will be preserved and used for the System URL. To read more about this feature along with instructions on how to try out the beta, please visit http://docs.whmcs.com/Version_7.0_Release_Notes.