Custom WHMCS & Cpanel Communication

I want WHMCS to create an account for Cpanel

but the only thing it can't do atm is generate a username (which it usually does) but I have a somewhat custom Cpanel module setup. No subdomain, No emails, etc and it's only for space. How do I tell WHMCS what username to use and how do I tell whmcs to send the clients email to cpanel (I need it so cpanel can generate a ftp account from that email)