I had this theory a long time ago on another forum. Actually, in order to strengthen the connection between Rikudo and Kushina in this case, you need to adjoin one thing: The name of the seventh path. WHen Konan was explaining Pain to Naruto, she said that Nagato himself was the seventh path. This seven path is also call Gedo if I recall correctly. Once you add this, it becomes clear that all the Jutsu made from that Gedo are the Jutsu that involve the user's life force. This is why the Jutsu of the seven path can lead to death if they are overused. I also think this is the reason why Obito's Rinnegan seems less powerful.
Kushina,s chain, Kushina's barriers, etc are Jutsu that Rikudo possessed to suppress the Juubi himself and lock him down. At least, this is what I think.