Invite Customers button should be available to all agents, not only administrators

When in any Service Desk project only the administrator has the option to invite a user (under people/customers).

Administrators aren't the ones answering the phone for new users, agents are. When they get a call they should have the ability to invite a new user and create the ticket on behalf of this user (hopefully in the same step).

When creating a ticket on behalf of a user that isn't in the customer list, an option should appear to invite that user as part of the creation of the ticket. One less step to go through.

In our environment, we have over 4000 customers and only a handful already exist in our portal. This would be a must for us (at least being able to invite the user we are creating the ticket for).

Thanks.