>I can't quite tell if it would allow plugins that don't also come from the Windows App Store.
I guess it wouldn't but I don't think it's problem. It's an opportunity for plugins to be easily discovered and restored. Opportunity for developers to make money on them (why not?)
>And, he might have to have the Backspace key close the app...?
WAT? Sure he doesn't.
>Not sure if it is allowed to launch a browser to external content (the help file).
Sure he can.