That's... exactly what the article is about. So yes, yes it would work.
Nonsense, the techniques outlined in the article will work with hundreds of routers. We used the WRT54 series router because it's one of the best selling home routers of all time.
Why turn it off? Because the article was specifically about turning an old router into a switch and if you don't need the extra Wi-Fi coverage there's no need to waste the power keeping the Wi-Fi radio on. We have written about what you suggest, Wi-Fi coverage via secondary router AP extension before though: http://www.howtogeek.com/104469/