I theorized a ways back on a potential way for Taylor to ReAdvent without having to mimic her original conditions by using the Heroic Spirit she canonically left behind, and that her Sin as a Beast might be Control.
Notably, even now, she has extreme difficulty with trusting others and not getting involved herself. Of not having direct influence on everything around her. She's deeply hesitant to let the twins out of her sight and is very uncomfortable when she can't directly fight because she can't have faith that things will be okay without her directly Controlling everything. It's a desire for Control borne of Worry and thus Love.
The Sins of Beasts we've seen so far: Pity, Regression, Lust, Love, Comparison, and Treasuring (I don't know what Nero Beast's is) are all common human emotional motivators that can result in monstrous behavior. "Emotional Traps" anyone can fall into and thus have to struggle to overcome, hence making them Sins of Humanity.
Actually, I agree that desire for control is the centerpiece of Taylor's motivations, which is why I didn't use it in my imaginary Beast!Taylor profile. I'm not really interested in a long philosophical search through her psyche, so I came up with another vaguely plausible possibility on the spot.
If you read between the lines, the Beast of Salvation isn't Khepri precisely, it's Memetic Escalation Queen Taylor progressed to the natural conclusion. Her Advent means something already went terribly wrong, and the humanity is almost absolutely sure to perish, which ties in with her personal history and the Sin I felt could plausibly fill in the seventh spot.
There's an inconsistent theme running in those Beast spots that have multiple candidates, like the fourth spot has a lot to do with demise of humanity as the dominant species of animals, ( which actually makes the Tunguska Lostbelt parallel the demise of dinosaurs from what I heard ) the third slot has to do with human love and alienation, and the sixth slot are blatantly Biblical Apocalyptic references. So the common theme I chose for the seventh slot is the existential horror of outer space, something arriving from beyond the stars or outside human perception, there's a fancy term for that in Nasuverse I don't remember, and demolishing humanity completely, like in FGO and a lot of other works in Nasuverse. I dunno what the deal with Olga Marie is, but Taylor's Advent is basically humanity changing irrevocably in the titanic effort to fight off the existential threat, so much so it can't be called humanity anymore, by either selfishly entrusting all their hopes and dreams on shoulders of one messianic figure or an otherwise unremarkable person taking the matters in their own hands and enforcing their will absolutely with the sole purpose of winning.
Salvation might not be the most appropriate word, but, like, what I was going for is the Nasuverse equivalent of the Indomitable Human Spirit meme. She's meant to mirror FGO Ritsuka, basically, a human who stands against the certain destruction, and does it again, again, and again. Which is, like many Evils of Man, isn't a bad thing in moderation, and indeed, Beast Khepri is meant to destroy the threat that was the Catalyst of her Advent… and then she'll find another. No Beasts left? Let's pick a fight with Oort Cloud. Somehow won against that? Gaia is kinda a bitch for calling all that shit on humans, isn't she? The world's dead, you say? I heard there's bunch of ultimate ones out there in the stars, just waiting for an excuse to destroy humanity, let's go fight them.
So yeah, Beast Khepri is a human Master who will do her damndest to depopulate the universe from all possible threats, and more likely than not will either kill all humans in endless conflicts or transform them in the ultimate warrior race with no free will, waging war against all existence.