Customizing RSS Feeds for Users

I’m playing around with the idea of using WordPress for distributing information in my corporate office, but I need to be able to restrict certain posts in certain categories to only be available to certain types of users. I’m pretty sure that I could write a plug-in to do this based on the new user permissions structure in WP1.6, but I’m not certain how to make this work in the various RSS feeds.

Here’s what I need to do:
1 – Be able to mark each post with an indication of whether it should be protected (the built-in password protection is not a practical option for my application). I would look at writing a plug-in to add this to the posting screens, storing the flag in a custom field.
2 – I would use Carthik’s Registered Only plugin to ensure that only registered users could see all the content.
3 – Using a plugin, custom template, or both I would filter out any content that doesn’t match what a logged-in user is allowed to see before any HTML is generated. This would be done by comparing the user’s permission in their profile in the v1.6 environment with the custom field in each post.

SO…..here’s the questions:
1 – To those familiar with WP1.6 Alpha code, does this sound like a reasonable approach to you?
2 – How the heck to I modify my RSS feeds to accomplish something similar?? (i.e. I would need to authenticate users to my feeds, which I think can only be done via .htaccess files currently — but then how can I filter data in the feeds, since I’m not comparing against a logged-in user that WP knows about??)

Opinions and feedback on this would be welcome, because if I can’t solve the feed issue WP may not be a great option for me…