WHMCS WP Integration – Single Sign On

I am working on a site for a client that uses WHMCS to manage their clients. The WHMCS WP Integration plugin is nice, but my client does not want to have to log in to WordPress and then use a different log in to access their WHMCS account. The page with the WHMCS shortcodes requires that the user is logged in to WordPress to access it.

Do you guys have a solution for this issue? If not, do you know of a way I can allow the site admin to tie together WordPress and WHMCS accounts so the user only needs to log in with their WordPress account?

Thank you.