Category-oriented MU BuddyPress site

Hello, all

it's my first post to the forums, so excuse me if I will be unclear or, you know, little lost.

OK, so here's the deal - I would like to create a multisite where categories would be the most important, mandatory thing in sites' structure. To that extend, that I want to allow my users to:

- subscribe to a certain category (so, basically, email notifications)
- follow a category (activity notifications)
- review a category and talk about it with other readers

For the subscription to a category I guess I will use Simple Email Subscriber, because WPMU DEV's Subscribe by Email allow only site-wide subscriptions and I wasn't able to ask via support box (it freezes after sending and that's it).

For following categories I would like to use BuddyPress Follow, but unfortunately category is not an object which following can be reffered to, am I right? But maybe if I would automatically create a buddypress group corresponding to the category and then publish a note on it everytime when admin posts something within this category? Maybe that would do the trick...

Anyway, how do you like the general idea? Did you see some sites like this?