I hate to admit I am one of the people who doesnt really 'get' the cookie in the middle.
I mean, I totally understand how it's done, but doesn't it make it really hard to cut the cake? Or does the icing cause the cookie to get kind of soft? Personally, I am addicted to sugar cookies with buttercream on them, so I can see how that would be delicious with a cake. I've seen so many people reference doing this, I've just not tried it because I was worried it would be a pain to cut... kind of smash up the whole cake. I guess I have to quit worrying about what might happen and just TRY it, right?
As for the bettercreme, I bet it would work, though I would worry about it squishing out when you cut. But that's me being paranoid.