Actually, having the Germans lose would be fairly easy. The Sukhomlinov strategy is one of the great underconsidered aspects of the war of 1914/15. He was the only military leader of the time to have truly adapted the insights of Jean Bloch into his approach, calling for a war of attrition that the Entente could have won. That is, of course, had anyone listened to him instead of betting on the likes of Foch and his ridiculous 'spirit of the attack' thing. The Entente weren't actually beaten in 1915 by any stretch of the imagination, they simply gave up. Though to be fair, nobody in his right mind had expected the punishing terms the Germans would impose on France. The Treaty of Metz was the start of the next war, surely.