I don’t know about that. The most significant part of the business requirements is not covered by Drupal core. Looking around it doesn’t look like any good, maintained membership modules exist for D7 either. Especially so with integration with a payment module. Unless it is PayPal you would probably be completely out of luck on that end.
Have you really already checked you cannot find all these features in Drupal 7 (or even with D6 as well) ? I have seen most of them in Drupal. Have you worked with Drupal before if yes then what kind of works you have done with it? If you had, then you must have found at least user sign up, content updates. How can you say that “you would probably be completely out of luck on that end”? I haven’t seen the payment option in registration that is only part that has to be looked into. Otherwise somehow either by using free modules or by modifying something in them can be achieved everything listed above in Drupal as far as I know.
Agreed on the payment part already in my last post which has to be customized by OP or still can be searched in the Drupal’s modules list. But rest of the features as far as I know are already in the Drupal system, aren’t they?
Our CMS has a paypal payments plugin we can provide, so your more than welcome to take a look at that.
Outside of that, I’d go for WP and extend it or even plunge on a commercial CMS like EE over Drupal or Joomla simply because they take a fair bit of work to get into.