Custom Contact Role field

We've added some extra Contact Roles into our setup (Setup>Sales Force Automation>CRM Lists), so that we can assign different roles a Contact has if they're in multiple Companies.  I've noticed that the 4 default Roles (Alternate Contact, Consultant, Decision Maker, Primary Contact) cannot be deleted.  Do these has special meaning in NetSuite? 

I tried setting up a new Custom field called Company Role, made it a List field that just contained all the new values we want to select from, but it seems the Contact Role field behaves differently than normal Entity fields.  My understanding of it is that the new Company Role is a static value (like phone number, address, or Name), and can't be modified on a per Customer basis.  Eg - We have some Contacts that work as consultants for multiple Customers.  Each Contact has a different Role while working with the Customer...so Contact A could have a Sales