You know what would have been a cool plot twist in supernatural?
If it turned out that nephilim aren't actually as powerful as all of the angels had always thought they were.
Like, think about it. Sam, Dean, Castiel, the angels, the demons, etc spend an entire season anticipating the birth of the most powerful being to ever exist—the offspring of an archangel and a human— right?
But instead, they get Jack. He's powerful enough to save Kelly from her suicide attempt and age his body and mind up to that of a teenager, but that might be the upper limit (and he didn't even do either of those things consciously). His birth still ends Kelly's life, but it doesn't open portals to a different universe. Jack still has powers, but his powers are about equal to the average angel. Maybe even slightly less than the average angel.
It's revealed that Chuck had forbade the angels from creating nephilim because he wanted to be the ONLY creator. He made up lies about nephilim being too-powerful abominations to ensure that the angels would always obey when it came to killing them.
So now, Cas and the rest of the angels need to reckon with the fact that they had murdered innocent children—innocent angelic fledgelings—in cold blood without a second thought.
Lucifer still kills Cas. But before he's able to kill the Winchesters and get to Jack, he vanishes.
When Cas is resurrected, another big plot twist is revealed. It's not Jack that resurrected him—it's Amara. While all of this was happening on earth, Amara was usurping Chuck. Amara is God now. She brought Lucifer's cage into Heaven—that's where Lucifer is now. Imprisoned again, but not in Hell. And not totally isolated like he had been for eons. Because Amara had been isolated in her own cage since the beginning of time and she knows how unspeakably wretched prolonged isolation is.
Cas tells Sam and Dean that Amara resurrected all of the angels. She restored everyone's grace and wings. And she gave all of them free will. Cas tells them that Amara told the angels the truth about Chuck and all of the lies and manipulations he's guilty of. She asked—not demanded, but asked—them to accept her as the new leader of Heaven, and in return she would be present, accessible, and receptive to their questions and concerns and ideas. The opposite of Chuck. Her one demand is an immediate end to angel-on-angel violence—including violence against nephilim.
And all of the angels, with their free will and newly restored grace and wings, did.
Amara also created more fledgelings. It's the first time in a long time there have been fledgelings in Heaven.
Jack is able to live and learn how to use his powers without the constant threat of other angels hunting him down. There's no danger of him accidentally causing massive destruction or ripping holes in time and space. Maybe Cas is able to take him to Heaven sometimes. Maybe Jack becomes friends with the other fledgelings and they play together in a freshly terraformed and restored Heaven.
But then there's a third twist: When Amara emptied out The Empty, she didn't just resurrect the angels. She also resurrected the demons.
There has to be balance, right?