So, here's an idea I had a while back; I posted it all the way back in May but it got no feedback (probably because it was at the bottom of a page), so I'm reposting it now (with minor edits) because I still really like the idea. I looked around and couldn't find rules against it; if I missed something somewhere, I apologize to the mods, and no hard feelings if you delete this repost. Anyway, here we go...
No Immunity
Metagame Premise: All immunities are negated.
How the Metagame Works: The premise is incredibly simple but it has a ton of competitive implications. Magearna goes from being immune to poison to being weak to it. Sableye is now dying to Close Combats. Better pack a Rapid Spinner to stop those Spikes from hitting your birds, good thing your opponent can't spinblock it! Tapu Koko giving you trouble, threatening to OHKO your Landorus-T with Thunderbolt? Paralyze it and call it a day. Should probably keep a Will-o-Wisp handy for when Charizard X switches in, too.
Potential Answers to Mechanics Questions: All immunities means all immunities - Levitate and Magnet Rise now do absolutely nothing, for example. In cases where it's an immunity + a second effect, the attack hits first and then the effect takes place. For example, let's say we have a Pokemon with Water Absorb being hit by a Water-type move. It will first take damage, and then after that (provided the damage didn't faint it), it'll then gain 25% of its max health. Also, moves that affect only a certain subset of Pokemon now affect everything. Hi there, Synchronoise! Finally, in case it wasn't clear, weaknesses and resists aren't negated, just immunities.
Potential Bans and Threats: For now, this meta will use the standard OU banlist, but with one exception: Arena Trap is banned even if the current suspect test ends with it still in OU. This meta makes it so it traps absolutely everything, even Ghosts! I don't really think I need to explain why that's stupidly busted. Other than that, maybe Tapu Koko since its Electric STAB is way more spammable now? I'm not 100% sold on it, though.
Questions For the Community: Does this seem like an interesting idea? If it does, should anything more be added to the initial banlist? Are there any mechanics questions you have that weren't addressed above? Anything else you could help me out with on this?
Thanks in advance for any feedback!