ARM & Blueprint Support for Creating Azure Active Directory Tenants
AAD tenancy as a bulkhead between service provider and customer is a key governance pattern. Microsoft itself recommends and uses this pattern to deliver many services including Azure.
Given the foundational nature of AAD and its implications on nearly all deployed resources, a Blueprint without the ability to create AAD tenants is like a book without a cover.
Having the ability to limit who can create an Azure Active Directory resource is critical for large regulated customers.