I read your fallen human masterpost. Are we positive that Frisk was the only one who woke up Chara? Could they have just been omitting unnecessary information when they were talking to the player in the genocide route? Is there any evidence in their narration that suggests that they have been through the underground before while accompanying the fallen humans since they also have determination? I love your theories! You guys stay awesome!
If Chara was awakened by any of the other fallen humans, then it would have been more than an omission. Chara outright states that they were confused upon waking up. The last thing they recall appears to be their plan failing. They also make it clear who brought them back to life.
Unfortunately, it’s difficult to use the narration as evidence since narrators tend to have omnipotence. Yet despite this, Chara as the narrator makes no reference to any of the other six fallen humans.