FSM6u10 Customer Portal Different Customers

I have a question regarding conditionally showing the ‘Create Request’ button on the ‘Service Requests’ screen of the customer portal.

In a nutshell, we service different customers (different organisations), some of which are allowed to create requests, but others not.  How do i achieve this on a customer by customer basis? the only way to do this i think would be by one of the following methods (if any of these possible)

1. All customers get the same ‘Requests’ screen but conditionally show the button
2. Each customer gets there own tailored ‘Requests’ screen
3. Have a separate instance of the Portal for each customer, who then access it with their custom URL