A cool idea I got after watching Shayy rank all the Neutral endings

Genocide: Frisk goes back, and throughout the journey they realize they did it wrong and try to eliminate chara (Boss fight).

Neutral: All fights become harder, especially Sans', making it almos impossible to fight them. (Maybe a union of Sans and Undyne in a fight against human. Flower doesn't try to kill you but jokes about how you fell down "You have enough power to defeat me and 6 human souls but can't avoid a f**king hole".

Pacifist: You try to defend your friends against lots of people that think monsters should die.

The neutral routes would be different due to the vast differences between the different neutral endings

There could be one where you go back to the underground and see that Mettaton has taken over and made it his own personal paradise

There could be another one where Undyne's army breaks the barrier and hunts you down

There's a lot of possibilities with the neutral endings

The lore is increasing

The Pacifist could be Frisk deciding to live in the underground and guiding the next human that falls.

True Pacifist could be what you suggested because it's a great idea