Using WP for a user database…

Okay, I really like wordpress so I thought maybe with some hacks and plugins it could make a great site for what I’m looking for. Here are the concise details.

The sites main feature is to have individuals subscribe to an email list. The form would have their name, two email addresses (this is a long term thing so I think they should give a back up email address), and then the name and email of one or two friends of theirs. With this data I’d like to send an email out four times a year that would go to them and their friends listed reminding one another to check in with the other (it’s for an accountability sort of a thing). So the email should include their names and email addresses.

Does that make sense? I think I could just hack the subscribe2.php plugin to get this to work, but maybe there is something better out there. I don’t want them updated everytime something is posted on the site, although that would be a cool added feature (though I won’t be posting a lot of stuff regularly). It’s mainly a data collecting site and email list.

Anyone have any suggestions?