Can I globally change the cmd-Q shortcut to require holding for two seconds, like the option in Chrome?
Here's a partial solution for starters:

Preventing accidental quitting in Safari (or any specific application)

Simply set up an unusual keyboard shortcut for the "Quit Safari" menu item in Keyboard preferences.

This will disable the standard ⌘Q shortcut, so accidentally hitting it doesn't make a difference — and you have to think before you quit!





(Unfortunately, I haven't found an easy way to do this for every application, without entering each one manually.)