Jiraiya said that the Kyuubi might of been a intentinel summoning. Maybe Pein was trying to get the 4th hokage for his "Jutsu"
Madrar summoned the fox becuase his chakra would be easier to get at if it were in a body (naruto). and then 4th sealed it in naruto thus killing himself. Well the Pein told Zetsu to gather the 4ths body after the burial or he switched it with his "technique" (like the fake itachi and Kisame)
and then pein has the 4ths body and can use it at will
he said i took out this body because i want to kill someone.
anyway i don't know everything and this is only speculation
but post what you think