Implementing Two-Stage Login

We are working on a project where the client wants the access to the CMS to be a two stage login process –

Stage 1) Initially a request for a generic username and password. This password can be saved in the Customer’s browsers password file – in which case it will not be necessary to re-enter this username/password unless changes occur.

Stage 2) Request for individual username and password. This password cannot be stored in the Customer’s browser password file. Whilst the username can be ‘remembered’ for conveniences sake, the password must be entered appropriately every time access is required.

What is the best way to implement this in WordPress? Thanks in advance for helping me out.

Mukul