on article https://www.whmcs.com/members/index.php/knowledgebase/14/Can-I-use-my-WHMCS-license-on-more-than-one-domain.html
this shows that multi-domain licenses can be added to WHMCS. I would like to see WHMCS go one step further by introducing native multi-brand support. For example
Client Group A = Brand A (whmcs runs from branda.com)
Client Group B = Brand B (whmcs runs from branda.com)
Then when welcome emails are sent things like $whmcs_url are replaced with the one from the client group (if applicable). If none specified then it uses the default WHMCS url.