5 Put back cool bars in IE -X2 - let us break it into pieces and put the pieces where - or back together how - we want. This wasnt done. Im assuming because they did not want tech support dealing with floating /embedded toolars / sections IE versions (id have loved it - tools on the bottom!
I don't see why you couldn't build a Windows 8 Xaml app with an appbar that accepts plugins via MEF or something. And if you have the unfortunate job of building the app in HTML5 you could use jQuery or something =)