In the Original Work, Nagato had developed his Rinnegan for over twenty years before he could use the Rinne Rebirth Technique.
Although Uchiha Obito had only recently received the Rinnegan, he had gained an understanding of the Power of All Creation through becoming the Ten-Tails Jinchuriki, then been controlled by Black Zetsu. Only then had he been able to use the Rinne Rebirth Technique to revive Uchiha Madara.
If anyone with the Rinnegan could trade their life for another's and revive the dead, Uchiha Madara would not have needed to seek out Nagato. He could have simply transplanted the Rinnegan into White Zetsu and had him revive him, couldn't he?
However, if Sarutobi Toru used the Spirit Transformation Technique to directly control White Zetsu, then as long as he had enough Chakra, he could use Rinne Rebirth. After all, it was fundamentally Sarutobi Toru casting it.
When the time came, the Pure Land of Ultimate Bliss would absorb White Zetsu's life force. What would that have to do with Sarutobi Toru?
This was the method Sarutobi Toru had devised to bypass the restriction.
After hearing Sarutobi Toru's words, Namikaze Minato did not ask how he planned to bypass it, nor did he care about Sarutobi Toru's current stance toward Konoha Village. He simply said, "What price do I have to pay for you to help me revive someone?"
Namikaze Minato was not the only one tempted. It could be said that every shinobi present felt the same.
Forget whether resurrection was a forbidden technique. The reason resurrection techniques were considered forbidden was that researching and using them required enormous sacrifices. If there were an easy way to revive someone, no shinobi would be foolish enough not to use it.
As always, shinobi did not exactly have high moral standards. Every