How to change domain mapping default redirect

When a user orders wordpress installation on my multisite install via WHMCS, the domain they enter gets automatically mapped. So far, that is OK. But the domain is not always ready on the server (due to registration/transfer process takin some hours). So therefore the customer logs in, uses the control panel and when checks the front-end gets redirectet to the domain (that is not working yet).

Therefore I want the original domain/user defined sub domain the be default when registering a new WP site on my multisite.

Look at this screenshot what config i want to make the default setting when ordering a new site via WHMCS.