Digital Signatures on Documents preventing Fraudulant transactions
When a customer purchases a product, the invoice sent to the email of the customer should have the option to digitally sign it, in response generating a copy of signed invoice being attached to the customer's account on WHMCS for every purchase. Thus helping in situations of fraud control and similar disputes.
There are multiple companies offering a solution of this kind, like RightSignature and DocuSign etc., they may be able to provide an API and a separate module enabling this can be added.
This can also be enhanced by adding additional documents like Terms and Condition agreement etc.