RSS Feeds in the web client. Of course this would be synced to the fat clients on the laptop/desktop. This way you can provide a single source for the user.
I want this, too. So that i can access my rss feed anywhere and on any device app. Should be synced to all Apps, like Outlook Deskop X86, Outlook Mail App Win10, Outllok iOS / Android / WindowsPhone App and on outlook.com web!