Interesting. I found one problem, though. (Or is it a feature?)

All examples I listened to of "coup de grâce" pronounced it /ku də ɡrɑː/, while the "correct" way (if there is such a thing)is /ku də ɡrɑs/.

This kind of thing must come up in more examples. I'm not usually on the prescriptive side of things, but I think it's important to know the "right" way to do things, at least when you're learning a language. On the other hand, hypercorrection will probably never disappear, so why not embrace it?