Newsletter/Email Management System

I'm looking for someone who has prior experience with email list management and e-newsletter delivery systems to augment my existing membership site. The existing website is built on Wordpress with Thesis as the theme. DigitalAccessPass plugin controls membership access and payment processing. I wish to add an automated email newsletter service, similar to Constant Contact, but with some unique twists. The goal is a service that a user can set up once and forget about, knowing that their newsletters will go out on a regular basis without their further involvement, OR that takes care of the bulk of their newsletter needs but gives them as much control as they desire. There are numerous open source and commercial newsletter management products available, but I have not found one that does everything I need. You must be able to review my specs (summarized below) and advise me regarding the best existing script to acquire that either (1) fulfills my specs entirely which you can install for me, or (2) fulfills most of my specs, but that you can install and customize to suit. I am open to a fully custom solution as well if it is the most cost-effective option. Summary of site specifications (subject to change): Users must have full control of their own mailing lists. They must be able to: - Import existing mailing lists - Build lists with single or double opt in - Grab a snippet of opt-in code (customizable) to install on their website - Select a weekly, bi-weekly or monthly newsletter schedule - Send adhoc broadcast emails in addition to the regular schedule - Export and download mailing lists The system must offer users a number of newsletter design templates to choose from. Users must be able to: - Select a template - Customize the color scheme, header and footer, etc - Input/modify their own data to be dynamically inserted into the template — Company name, logo and other graphics, mailing address, URL, etc — From and reply-to email addresses — Affiliate links for any products mentioned in the content The newsletters will be supplied to users complete with pre-existing content (produced by my staff) that will merge dynamically with the users’ data to create a unique newsletter each week for each user. Administrators must be able to: - Upload articles and graphics - Modify content as needed - Queue newsletters for distribution - Queue preview sent to user for approval 48 hours prior to distribution with note from Admin (e.g., “Here is a preview of your newsletter scheduled for Monday 9am EST. If you wish to make any changes…”) Users must be able to: - Select full automation or manual approval - Choose full text or digest formats - Edit or remove any supplied content - Add new content of their own - Cancel or reschedule any individual newsletter To apply for this project, please provide URLs of sites you have worked on that include similar functionality. Include the software environments you prefer to work with, and any initial advice or recommendations you are comfortable offering at this stage. Estimate the time it will take you to complete this, along with a project price. If you are available for post-implementation maintenance and upgrades, please include your hourly rate as well.