1. It seems we failed to completely fix https://bugs.kde.org/show_bug.cgi?id=423035 for years. And I guess part of the problem is the screen turning back when the user releases the hotkey. A button should fix that. We can even make sure it does by adding a small delay before turning off the screen. 2. It seems logical to have an "off" option in an applet where you can adjust brightness. Just as the volume applet has a "mute" option. 3. The applet has plenty of space to add that.
Yeah, seems reasonable. The applet does have a lot of space now, especially in Plasma 6.