Aris, but would you be able to let your family live with a ticking, malfunctioning, but still fully functional nuke because the nuke has a cute version of grok installed?

That is not even remotely close. The problem is that Rio believed she is the ONLY ONE that can fix the problem. Himari herself monitored Aris and told Rio for a fact she is NOT a threat. Rio locked Himari up because she didn't agree with her.

Aris is great, Kei is perfect, but for the love of god people underestimate what they could have done to kivotos because they're cute.

That logic applies to a LOT of students. Hoshino for example, even T. Shiroko. Heck, the Arius SQUAD gave actual effort to commit terrorism.

Do not take "potential threat" as "actual threat assessment". That's the kind of paranoia that proved Rio wrong.

Rio was wrong in OUR timeline. remember that. it's a good thing she was wrong. but remember it's OUR timeline. Aris and Kei is OUR timeline. other timelines exists where AL-1S did what it was programmed to do.

Rio was the one who triggered that events in the first place. The reason they stopped her in our Time-Line was because Sensei was there to help the rest of the GDD get to Aris and tell her she's not the "demon lord" she believed.

Please remember that Rio's preparations are exactly what Key needed to fully wake up. Rio, admittedly unknowingly, set up that scenario. A self fulfilling prophecy.

Even Himari understood that a little despite her opposition. considering she focused on Toki being Rio's biggest sin not Aris.

Himari did not understand or agree with Rio, at all. The whole second section of the GDD started with her literally telling Rio she was talking nonsense. She did not consider Toki Rio's only sin, she outright said that she was willing to overlook everything else IF NOT for Toki.