Get Orders from External Ressource

As I understood, in order to register an order from external ressource in Shopware is necessary first to register a new customer and then attach the order to this customer. The field  “customerId”  in the POST order query is mandatory. 

In Orders response from OTTO there is no cutomer data but could be used the date from ‘invoiceAddress’.  The problme is that there is missing the email address which is mandatory for customer registration in Shopware. 

I am thinking now of creating a single customer for OTTO in Shopware, so that for all OTTO orders will be used just one " cusomerId".  But there will be different data ffor billing and delivery for each order.
Is this a good solution?