For the RSS options add a forced redirect so that any "sub feed" gets redirected to the main feed.
Main feed: domain.com/feed/
Or: doman.com/category/blah/feed/ (etc.)
Only the main feed should be available.
A exception box and perhaps custom RSS url box can be options of this feature.
Exceptions for the 1% of people who want /feed/ links to certain pages or categories.
Custom url for if you're not relying on the WP rss engine, but say Feedburner.
Why do i want/need this feature?
People are enmasse subscribing to /feed/'s on tags, categories, old posts... They should be on my main feed. They're missing out on my posts and it just looks messy.
I believe that one or 2 (posts/comments) feeds is plenty for most sites and this will improve the Sites SEO a bit too i think.