Iniesta vs Kroos was a though one. Alves vs Carvajal was easy. If you have Messi you need to have Alves as well in the right. If you have Alves on the right, you can't have Marcelo on the left (that means Alba takes his place). Ramos vs Varane was difficult, but Ramos is a leader and would form an amazing pair with Pique, Modric would also be amazing as a clasic CM I think (more of a playmaking position than the one he's playing atm). MSN is a given up front (sorry James -- the most unlucky player in this situation).
Bravo vs Navas is 50-50, Navas is more spectacular, but Bravo is one of the keepers you can trust the most in today's football. Most of Real's fans will say Navas, most of Barca's should say Bravo. You can pick either one I think and be happy with your choice, as they are the 2 best keepers in La Liga, very close in value.