Earlier quoted context omitted.
I find it odd that your first comment is a complaint that setting up a new user actually acts like a new user. Of course your settings didn't carry over. That's the whole point of separate user accounts. I see no need to overcomplicate it. A user account system where each account acts like a separate device (aside from the unfortunate realities of sharing storage resources) would be fine. What apps share state? None!…
On fixed hardware devices things are a bit easier, but consider a desktop PC with Windows. If i install a driver for my new printer, should user B also have to install that driver? Should every family member have to install a printer driver?! To make things even worse replace printer with something necessary to even run the system properly like graphics card driver. Another food for thought is windows update. I consi…
The idea that keyboard localization should be system-wide is weird. Different people can speak and write different languages. Although it should be a non-issue, since a single person can speak and write multiple languages, and switching keyboards should be trivial.
Anyway, you can come up with scenarios where my "make it act like a fresh device" idea is inadequate. But my idea is still an absolute improvement over what we have now, and would be perfectly good for a lot of uses. You're describing a bunch of stuff you want but that is by no means required, and then using the complexity of that stuff to say that the whole feature is a bad idea. It doesn't make a lot of sense.