If you use the Windows+# shortcuts it's pretty easy to navigate multiple instances of an application. I don't know how the ordering works with the centered start button, but traditionally, the left-most application can be switched to by pushing Win+1. The second instance of the first can be switched to by holding Win and then pushing 1 twice. That's been available since Vista.
I don't want to excuse taking options away from users, but there are workarounds.