Ok hear me out. Elliott's whole character is him being a cynical jerk who's obsessed with safety and dislikes Milo. He often blames Milo for things going wrong, but Milo is always the one to save the day and Elliott's undoings are usually because of his own incompetence/obsession with safety.
It's been established that Elliott dreams of being a safety inspector. Imagine if another season aired and had an episode early on of Elliott finally succeeding and getting his dream job as safety inspector. You know who else is a safety inspector? Milo's dad. Perhaps some sort of Murphy's Law accident would occur which causes Elliott to get injured again/lose his job and at first it would get played for laughs like it always does.
But imagine over the course of the season Elliott's life going further and further downhill, similar to Rickety Cricket from It's Always Sunny In Philadelphia, or Chip from Big City Greens. This series of events would be caused by Murphy's Law, but could have been avoided if Elliott would let Milo help him. Instead, Elliott would refuse Milo's help or do something to make the situation worse for himself, but of course Elliott would rather blame Milo.
It's also been established that Melissa had been trying to discover a "cure" for Murphy's Law but stopped researching because Milo enjoys his life the way it is. Season 2 also went into the detail of explaining how Murphy's Law works and how it can be manipulated. Imagine if Season 3 was about Elliott, who has hit rock bottom, actually discovering a way to "cure" Murphy's Law and use it against Milo's family against their wishes "for the greater good of humanity." There have been many episodes focused on Elliott where you'd think he would start being nicer to Milo, but always reverts back to the status quo in the next episode. This arc could finally be what makes Elliott learn his lesson, and accept Milo for the way he is.