So by "producer" they mean "stylist"? If so, Ayumi would be a great choice.

once again, ayu is in the top! thanks for sharing

Haha the girls would probably like to be produced by someone who was just like them when she was discovered and shot to fame. Of course, ayu would have had a much more bumpy road but with her track record as a singer, i would trust her to maybe be more of an advisor than a producer. But that's totally something can think of branching into when she is less inclined to being a recording artist.