How can we improve WHMCS?

We would like to propose an API call that would accept pretty much the same arguments as the AddOrder (https://developers.whmcs.com/api-reference/addorder/) API call (customer details, address, product id, addons, etc, etc) and would return back a "fictional" invoice (total amount, taxes, invoice line items) that would contain the total amount due of the order that would normally be created if the AddOrder API would have been called.

We believe this call would be helpful in cases where ordering is performed outside WHMCS via the API module and the integration solution would like to show to the customer how much the order would cost, if the order would have been be submitted, without actually creating the order

Thank you!