Looking for a subscriber list management system

Even I placed a lot of questions back to your question, I would like to share the following idea:

This basically sounds to me that users are subscribing to a post (maybe of a custom post type and with a custom taxnomoy). So to replace the comment form with a subscription form and to use comment “subscriptions” as “post subscriptions”. That for re-using the database.

Next to that, this would need some backend to handle daily jobs in the admin.

I’m not aware that any plugin is already offering this. But probably if you get a bit more flexible with your needs you can find some components you can mash-up into something what you’re looking for without the need of much coding.