You are expecting Microsoft to be a vertical solutions provider. For years people have noted that while Exchange does basic email and calendaring they have thankfully left some crumbs for developers to add features that you noted.

Your list of items are not omissions in the Exchange product as I see it but then again I am both a programmer and am aware of Lotus Notes and more.

Let me directly address item 1. That concept of permission to edit documents is a throwback to pre-PC (Personal Computer) days where you had a mainframe with strict limits on what we allowed the users to do.

The PC (remember Personal Computer?) liberated us from that tyranny.