From the UX point of view, what we suggest is the classic onboarding experience where an organization admin invites new members via email to the organization (a hub for instance in the OFN case).
The new members receive an email and they can join the hub and start buying.
This would be the easiest to implement as it doesn’t add any UI element, we just send an email to notify people that they have been added to a hub in this thing called OFN.
The other way, adding a button on the create customer form can be more intrusive since we need to actually add a button.
In both cases I don’t think that we need to apply this change only to “customer only” enterprises since in any case the admins will have to willingly create a new customer from /admin.
In any case we need to better understand the relationship between a User and a Customer, both in the product and in the code. And in which case we can assume that a Customer is also a member of the enterprise or just a customer.