I think, just two games in, that replacing Hart is the right thing to do. You can see clearly that his passing from the back will lose us possession several times a game. And it's obvious that part of the passing game plan is to not be afraid to go backwards if necessary. You can't have any weak point in this system, which is why the likes of Mangala won't fit in.
I'm hugely impressed by the way Pep has bitten the bullet on the dead wood: Ya Ya, Nasri, Bony and Mangala....and Hart, whilst dead wood sounds harsh because he's a top class keeper. That shows strong leadership, and he's made exactly the right calls (apart from Kolorov, although there's time!).