I would love to see the possibility to have single-signon capabilities for the enduser panel.
it would be a great deal to get rid of the WHMCS module (where we constantly need to keep up with the changes/customization). With single-signon, users could click a link in whmcs or other billing software clientarea and open up the enduser panel.
It is done with CPanel and it would be great to see that feature with Virtualizor too.