I have very mixed feelings about Superman running a DC equivalent of The Authority. In many respects, The Authority represent the antithesis of what Superman is meant to stand for as a superhero. I haven't read many Authority comics, but from my understanding, the gist of The Authority is that they will use any means to get the job done, including disregarding politics and killing villains, whereas Superman adheres to his personal moral code and tends to respect international law and borders. The point of the Authority was that they were essentially a critique of the traditional superhero formula and that superheroes should act more proactively in dealing with crises. As for Clark working with Manchester Black, I really can't see how that would work.
Since Death Metal has supposedly made everything in DC's history canon, Clark would remember that Black has; tried to kill him along with the original Elite and almost convinced the public at the time that their methods were better at solving problems, revealed Superman's secret identity to the world and threatened everyone Clark cared about along with trying to get Superman to kill him by a telepathic illusion of a dead Lois. Not to mention the fact that the last time Superman encountered Black, he was in control of Hamilton County and was trying to brainwash Jon into crossing the lines that Superman wouldn't. Also, since Black's mind was stuck inside a cow's during Black Dawn, I'm not sure Black would want to work with Superman after that embarrassment.
It bums me out that I can't get excited for this series. Grant Morrison is my favourite comic writer, and they've written some of my favourite comics of all time. Manchester Black is one of my favourite Superman villains and I've been interested to see how Superman would interact with the DC versions of Apollo and Midnighter for a long time. But despite all that, I'm not sure I'll be getting this comic.