Why? They have different goals, Team Magma wants to expand the land what makes them Eco-terrorists (through they are ignoring that the land can't live without the ocean because they are a bunch of idiots). Team Rockets ambitions go from making money out of evil deeds to world domination, sometimes also searching for Giovannis child, depending on what source/time you refer to. In the Adventures manga Marco and Maxie temporarily join forces to get to the ground of the ocean and to fight off Ruby and Sapphire, but due to their opposing goals they are enemies. But Magma and Rocket? Team Rocket should be clever enough to know the immense land expansion would practically cause the apocalypse to happen and then there will be no money, no lost son and no folks to rule over. I can image Team Magma trying to use Team Rocket's resources, but not why the latter ones should let that happen.
Also, where does those two teams come from? In the traditional games both Teams were disbanded. So does Team Chaos only consists of strayers who are sad that good ol' playtime is over? Just a bunch of (traditionally) weak people causing minor havoc the local police is unable to handle? If the teams weren't disbanded, why not and [see joining issues above].
"Volcano of Doom" is a unusual name for the free-healthcare-world of Pokemon. And what does the Shadow Elixir have to do with Team Chaos? Do you have to feed it to them so they become good again? Who made it? How did the protagonists get wind of this ominous elixir?
Please tell us more about how the protagonist is awesome and the only one to stop the catastrophe from the very beginning. Red was a nobody who happened to train himself strong and happened to run over Team Rocket a dozen of times. Same goes for Gold. Ruby was the child of a gym leader, but his family was new to the region so nobody knew him. Ruby ran into Team Magma/Aqua a dozen times, happened to have the red/blue jewel and this was enough for Steven to let him meet up with Groundon/Kyogre. (By using the name of the male main character I just meant the player character.) I don't know about the following games, but I would be surprised to find it very different from this.
But since brother and father are well-known and long enough there to make a vacation, I guess NPCs would known the little one after all. Did you considered that? That can still make a great aspect of the game, everyone pressuring the protagonist because of his family, so he has to prove himself.
Side note: It is never the mother to be out on an adventure.
And nice talking like "Please don't stop me from stopping the end of the world, I'm the chosen one." won't work, huh? You make it sound like rival WANTS Team Chaos to succeed. (Whatever it is they want to accomplish.)
Fighting smashes rock and that was it. What about Dark-Psychic-Ghost or Ice-Grass-Rock?
elarmasecretas changes would reduce the choice to the types. So, a triangle of forces plus Electricity weak against Grass, strong against Water and Fighting not involved in balancing at all? Questionable. I would prefer a cool Trio-Combo.
Did I good?
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