Re: Um, just NO!
Apple allow you to download the install image from the App store and transfer it on to a USB stick, so that is an option if you have a working computer.
If you don't have a working computer that can download things from the App store, or you CBA to fish out a USB stick from the bottom of your box of computer junk, then cloud restore is another option.
Another thing, can we have a Windows version of Time Machine. On a Mac, you can restore a b0rked comupter in a few clicks plus however long it takes your NAS to transfer the backup image.