Okay this idea may seem absurd but I think smogon just automatically put him in the ubers tier due to his legendary status and his ridiculously high stats without any thinking and without realizing its flaws. Well first Rayquaza may have the best offensive stats, movepool, and may be the best wallbreaker/mixed sweeper in the game but base 95 spd is nothing special and gets destroyed by ice shard. And his defenses arent that great to take hard hits either especially when you are running a -Def or -SpDef nature if your going to make him mixed. So a faster sweeper can easily destroy Rayquaza actually. More so he is limited on switching because of its stealth rock weakness. I think he is perfect for OU. Kind of like Slaking who has high stats but in a low tier because of its bad ability. Also, he might have extremespeed but not enough to KO any ice poke like Weavile(Weavile ice shard goes first anyway) or Mamoswine or any dragons without a boost. And if hes going to be boosting, then they will use that chance to kill off Rayquaza. So therefore his monstrous offensive stats will be wasted if he will get KOed before he attacks.
So how about us allowing to use Rayquaza in OU JUST when we're battling each other in this forum or if others accept it? And seriously, do we really need to follow smogon on what tier he is being put in, a different forum? And one last thing, THIS IS A RAYQUAZA FORUM!!! So shouldn't we have freedom with this precious poke that is the representative of this site?
Btw I would do this and ONLY this moveset if I were to use Rayquaza in OU.
Evs:252Hp/4Def/252Spd(No offensive investments)