I still think that Ciro set up the plan and Oric took credit for it somehow.
Ciro's outburst after being resurrected seemed to imply that Ciro knew what was supposed to happen.
It seems to me the point of the plan wasn't simply supposed to provide Soul Charge to the underworld but to also provide longer lifespans for the crew.
We were told by Yaos that people like him would suffer early deaths. Most likely from using their Soul Charge without realizing that they were using it. Yaos specifically mentions that his powers were the same but amplified. So I would guess that their powers still drained Soul Charge even then.
Now Oric, Ciro, and the rest of their crew intended to put together a system that could keep themselves alive, but Oric betrayed them all. Oric wanted to provide himself with unlimited life. Cain implied that there are other possible candidates to be siblings, but not all are chosen. We also know that the Blue Chick, now finally confirmed as the Eye, hasn't been a sibling for more than 3 cycles from what Betweenford said to her. But Ciro had some sort of flashback when she met her.
Eh... I'm no longer sure about anything.
According to Cain's Storytelling, each of the Siblings has been a "Sinister Sibling" since Oric enacted his first plan. The plan was to use one of the Siblings(Target) to experience feelings by exploring and conquering the Warrens. Ultimately, the target would kill a bunch of Siblings and die. The Siblings would also experience feelings, then die by the hand of Target. Once Target got to the end of the "adventure" Target would presumably die by the hands of an Angel/Oric, and the Soul Charge would be harvested. After the death of Target&Company, Target and all the Siblings that had died would be revived in a supervised LSS, memory wiped of the events which occurred, except a select few memories
(YOU ARE THIS BOY/GIRL, YOU HAVE BEEN EXPLORING FOR SOME TIME). The revived siblings are deposited into their respective DL's, given orders; and Target gets dumped into DL1, ready to start over again.
We know these events as a "cycle". This was Oric's plan. Judging by what Cain said about his plan(KILL AND EAT, KILL AND EAT), the Angels knew they were looking for someone with a plan that would work, and probably heard the plans of each of the Siblings; ultimately deciding Oric's was the most ingenious. (target's plan probably would've been something with hoarding)
Oric's plan however came with him probably not dying at the end, and the Angels didn't think that was necessary, so they fired him. Yada yada yada, immortal beings slain. Oric gets rid of the Seraphim, except for one. Without the immortal being having to constantly eat, where do you think the Charge goes? Directly to Oric, that where. Judging by how FFS said that Oric's sin was gluttony, it would make sense that he would feed off the Soul Charge that would've gone to the six slain Seraphs.
The Oric Plan was for Oric to feed the denizens of the Underworld(Angels/UnseenHorrors); with 6 of those slain, and 1 left mutilated(probably feeds it only enough charge to keep it alive), he gets almost everything(after feeding whatever powers the Warrens itself). Oric would be the only one able to live a longer life.(Think of it like having to feed a Household of 8, if 6 of them die, and 1 is left in life-support; then you don't have to pay as much to feed them, after taxes of course). With his siblings constantly dying around him.
There have been at least 1000 cycles, going directly off what the coded transmission said. That means after Three Target deaths, Floe has been alive. She was said by Cain to change very little in between her deaths; she was presumably killed last by Minus. Voice had installed a plan though, for Target. He installed a way for Target to remember past cycles.(
T-MiNuS 120/TMNS120)
Cain is imprisoned for trying to break the cycles, and doing what he does best: Murder. He killed Mechanic, and presumably other Siblings. For doing that, he gets imprisoned, with his Soul taken away so he could do less damage.
The issue with this is that Cain is filled with seething rage, rage equals Soul Charge. Cain probably is a pot boiling over when it comes to Soul Charge. This is why Cain is dangerous, this is why Cain can break through his shield occasionally. And judging by his innermost passions, his Star probably let's him murder people pretty quickly in weapon form. This is probably also why he can't become Willborn, let alone Illborn; due to a constant RAEG for Oric. Moral of this tangent:don't let Cain free, unless you want to see some carnage.
Yaos' story is interesting however. It implies that although most of the Siblings/Gifted were able to channel their Souls to do impossible tasks; we know these tasks to be fueled by their Souls. With a drained Soul, a formed Gifted Generic would probably be easily killed. His powers were amplified through his Star, becoming the focus of his power, at the cost of accelerated loss of Charge.
Each of the Sinister Siblings are destined to stay in Oric's cycles, ultimately being slain. This can
ultimately probably be explained using a
Food Pyramid/Energy Pyramid.