Drupal - Mailchimp Webform Module modification

A client wants to integrate their Mailchimp lists with Drupal. Drupal has 2 modules to do this: 1. Mailchimp module - integrates the user registration form with Mailchimp so when users register, they can choose which lists they want to subscribe to at the same time (all lists are shown as check box choices in the registration form). 2. Mailchimp webform module - This takes the first module a step further by exposing a "Mailchimp" field on a webform. You can then very easily tie that webform to a Mailchimp list. However, this method only allows users to subscribe to that single list associated with the webform (1 to 1 relationship). The catch is that they want to allow for multi-list registration (like the Mailchimp module has) from within the webform because they don't want users to create user records on the system. I would like to integrate the functionality of the multi-list registration into the Mailchimp webform module so user can view all of the lists from the webform (as check boxes) and choose which ones to subscribe to. The following URL shows someone who was trying to do something slightly different but it illustrates some of the hooks and ways to build the data to send to Mailchimp: [login to view URL] The client is running Drupal 6.