You need to change the standard procedure of ordering Bitrix, change the settings of the component sale.order.ajax so that on the checkout page should be only part of the Buyer and shipping.
The meaning of this when placing the order it was created as unpaid, and then the content Manager can change the status in the administrative section.
I disabled the payment system on the side of the administrative section:
Store->Settings->order Properties->List properties
But now when ordering you will receive a message error: joxi.ru/YmE13qpf0NZMwm