It would be a damn cool OS feature to remember all the documents and applications I have up, where they are arranged, and allow me to take a "snapshot" when it is all ready to go.
In windows, it's called "Hibernate".
Go to where ever windows put the shutdown UI and click on it. There should be a few popup options, Switch user, Log off, Lock, Restart, Sleep and "Hibernate". If you don't see the option, go to power settings and advances power option. Turn off Allow hybrid sleep. In newer windows you might also need to turn on showing that option in the power options menu.
"Hibernate" hibernates your pc with everything you've opened. Upon booting up, it restore all the documents and applications you have up at the time. Unlike 'Sleep' once you've power down, you can disconnect your pc from power until you power it up again.
Hibernate is also the technology Windows 8+ uses to boot faster, since it never truly did real startup from fresh.
Back to topic, MS already have a solution to their problem, but I can guess that they are still planning to create something meaningless. Just like the Metro menu which if you look closer, is just the desktop with bigger icons. They could have just improved the desktop, but no they decided to create yet another desktop and called it the start menu. You can probably guess what they will do with the "single-window experience".