Lovely theory! Pretty much explains how I understood the entire Rewrite story. As for whether Sakuya and Kotarou are incarnations of aurora, I still have some doubt about it but it is a likely one. I think the sentence below says something about it too.
My thoughts on Sakuya and Kotarou (the Rewriters) is that they are superhuman who has the ability to manipulate the very essence that made them, i.e. lifeforce/aurora.
And something about Sakura, anyone knows how she found out what Kagari is doing? My understanding is that she is like the pinnacle of human intelligence or the human species to fully understand aurora and she realized in one of the world that she is in a simulation and somehow manage to break through the simulation (reminds me of the real-life question of “Are we living in a simulation?”). She probably found out Moon through Kotarou as stated below:
Yep, Oppai Ending was good, but it probably is a failed one too because the main point (Terra/Oppai Spoilers) [spoiler] is not about letting Earth survives because it will eventually dies when Sun uses up all its fuel, and all life will be wiped out. It is about letting intelligence life continues on, so intelligence life in Earth need to go out into space and find a way to live there or colonize other planets. Oppai route did mention about humanity building some sort of oppai spaceship to explore the universe, but it probably failed too, because, this is just my speculations, the technology to harness lifeforce/aurora is not understood enough or known to the public. In Terra, Kotarou Faction leaked out everything about Gaia and Guardian, which includes the technology to harness their own lifeforce/aurora. I think this is the key part in colonizing space?
Hey, maybe because Kagari just hate it so she kills off that branch XD [/spoiler]