As a consultancy, we have found that our client related work is best captured as a circle per client. Very often we (re)use the same roles across multiple client sub-circles of our Delivery & Customer Care -circle, ex: ScrumMaster, Developer and Customer Caretaker.
We have captured these "role templates" in separate documents on our Google drive and implemented a policy on our Delivery & Customer Care -circle that changes to these templates requires the governance process.
The client sub-circle of the Delivery & Customer Care -circle can choose to create roles based on these role templates, but nothing prevents them from choosing to establish other roles, change their concrete roles or scrap them all together.
This allows for a discussion on what do we generally expect of, let's say, a Developer in a client project, while still retaining the actual authority for defining roles in a client sub-circle - at the sub-circle's governance meetings, where it belongs
I remember Brian Robertson mentioning (on the Scrum Gathering in Prague past November) that role-templates or another solution to this tension is "in the working" for a future revision of the constitution. Mayhaps someone from HolacracyOne can elaborate on this?
Would love to hear how other people are dealing with the tension of wanting to reuse roles while not violating the circles authority to define their own and make changes to these reusable roles.