We already have the printerfriendly skin and the link at the bottom of any page for a printer friendly view so I don't think we need that.
I think if we are going to implement some kind of email this page to a friend feature, it should be implemented as a control that can be re-used across features or pages rather than implementing it inside the RSS feature itself.
If you want to try and make the rest of those improvements its fine with me. I would say go ahead and do it in the existing feature as I'm not opposed to any of those enhancements. When you are finished you can send me the changed files and I'll review it. If for any reason you end up with something I don't want to include back in the project, you can always clone it at that time to make your own feature and then revert the original.
One feature I would love to see in the RSS module or possible in a new different RSS feature would be the ability to have a feature where you could subscribe to a whole bunch of feeds and then selectively publish individual items from any of those feeds. So only the admin or editor would see all the subscribed feeds and the public side would show only posts approved by the editor.
Also would be good if we could support atom feeds in addition to RSS. I looked at this project a while back and it looks useful for managing all kinds of feeds.
I am swamped so I can't get to this stuff right now.