According to me, Alaia never understood Vionnet. He creates conscious-form clothes but he forgets the freedom of the body which was essential to Vionnet.
I think it would be a great challenge for Tom Ford and that we would have the vision to make Vionnet match Chanel in less than ten years... Chanel was also a dormant fashion house before Karl Lagerfeld came... I know that when Tom Ford was at St Laurent, he was always talking about the vision and the cut of Vionnet, so, it could make great sense for the House to have him as Art Director...
Sophia Kokosalaki is a woman, like Madeleine Vionnet, she is influenced by Greece, like Madeleine Vionnet, she has great technique, like Madeleine Vionnet, she is a great inventor, like Madeleine Vionnet, she does not like to be too much under the spotlights, like Madeleine Vionnet and last but not least, she claims Madeleine Vionnet is her major influence. So, there are many good reasons to pick her.
B) Karl Lagerfeld has an immense knowledge of Vionnet and he copied her a lot at his beginnings. I think he would be able to catch Vionnet's vision and dress up this vision with much talent. I believe that for him, it would represent its life achievement... He would have headed Chanel and Vionnet, the founding myths of modern fashion culture.
Pecoraro is not even to be considered.
Zac Posen could wake up the fashion house but I don't think it would be a relevant choice in the long term.
Olivier Theyskens is already waking up Rochas, which is nothing in fashion history compared to Vionnet. Vionnet would be a more decent job for him... Maybe, he could be much more inspired too. Its seems he has lost most of his inspiration since he joined Rochas...