WHMCS content untouched by theme css

Basically I plan to install WHMCS integration on several wordpress sites, each with their own themes for branding.

It is to difficult to manually go in and correct the various issued caused by the theme css changing the look of the WHMCS content. I want the WHMCS content to look exactly the same as if you went directly to the whmcs directory itself.

Essentially, I want the WHMCS content to act as a iframe for the whmcs content only, with the rest of the page in sync with the wordpress theme. I would use the iframe, but ssl will not work with it.

To achieve this I need the css of the whmcs content to be untouched by the any other css sheet and the default WHMCS css downloaded from the site.

Is there anyway to achieve this?