In your opinion, what do you believe would have been the result of the battle on the Blackwater if Stannis army had actually achieved a crossing, got most of his army across, but still had to content with the arrival of the Lannister/Tyrell army that arrives? He doesn’t get caught by the largest section of the newly arrived army, and instead faces of against Tywin’s force chiefly. However, it seems to me impossible to retreat once already across.