My younger brother decided to
sudo rm -r /Applications/System\ Preferences.app. Yeah, it was a pretty stupid thing to do.
(In his defense, it's probably my fault for giving him bad habits--whenever I set up new macs, I always forcibly remove iTunes, Chess, and other preinstalled applications that I consider useless.)
He is currently running MacOS Sierra, and aside from the fact that he can't change any settings, his computer appears to be running fine.
I told my brother to redownload the Sierra installer from the Mac App Store, use Pacifist to extract the System Preferences application, and copy it back to his applications folder.
He did so, but the newly-extracted System Preferences app doesn't work. It opens, but displays a blank window with no preference panes to click on. I advised him to do a reinstall, but he doesn't want to.
How can my brother get System Preferences back?