Forcing the use of a shared address book

I have a client with an interesting request that I really have no solution for.

They want to consolidate all of their personal contacts into a single address list with sub folders, and force all users to use that as the default address list which is then managed by 2 users. In this, they want to REMOVE the personal address book for each user and set this shared address book as the default. I am thinking a public folder address book is best? What is the suggestion for this? I have never had a request like this.Secondly- how can I (from a server level) force users to use a specific address book?

Thanks in advance for any tips or pointers- this one has me stumped.