Sixpaths I'm well aware of your argument, but we still don't know how it's going to work out or whether you are right or wrong.
He needed the death god because he couldn't seal the entire thing in Naruto. Not everyone is a suitable host for bijuu and Minato was not, otherwise he would have not used the death god.
If you simply read the chapter you see him pull out the kyuubi's chakra, it enter his stomach and a seal pattern form on his stomach, the same exact seal pattern that is on Naruto's stomach. This is why I think it's possible it's still sealed within him. Judging by what happened when Orochimaru cut open the shinigami's stomach, it must be somewhere. We saw 5 things come out and they were the 4 hokages and Orochimaru's arms. If it was simply in the death god then where was it when he cut open the stomach?