A few things on this for me:

The Admin role really needs splitting as most companies have IT Support departments that are responsible for granting user access and general managing of permissions. We don't want them to have access to business rules, tickets or customer information by default. Yes, I know they could create a user to do all of those things, but it shouldn't be the default position of an admin.

Charging full agent price for users that don't use any Zendesk functionality is ridiculous. I want my IT Support team to do the above user admin but it would cost us £360 a month just to do that.

Having a single owner is also very bad practice. It leads to either shared credentials or having a single point of failure.