Not to disregard your remarks, I suspect they are valid, but they come from habits of uses of others systems, and there's also the good practice to avoid introducing too much ways to do the same thing, because it's dramatically augments your chances that it is known by all (in the end), works well and as expected.

Hence launchpad is only here to shortcut finding your apps in the finder or the dock, mission control just an increment over spaces. Those are not replacement for dock. So quitting app, aside the app shortcut and menu, goes through the dock, either by dock app menu or ⌘+Q on the ⌘+tab app switcher.