Board Thread:Theories and Speculation/@comment-5413572-20151114042410/@comment-1210805-20151114115343

Creating Kaguya seemed to require recreating Hagoromo and then adding the full Shinju. Hagoromo was more than just his eyes, so summoning the statue would only accomplish a small part of Zetsu's plan. If all he needed was the Rinnegan, the statue and the tailed beasts then he probably would have spent more time manipulating Nagato, rather than continuing to use Obito, and by extension, Madara.