The problem with a die-hard definition of OU is that back when it was first established, we had only two Ubers who didn't even had a proper tier to roam free: Mewtwo and Mew. So OU really was the "first balanced metagame possible" (some people will disagree and say Tauros and Sleep were broken but roll with me here). GSC had mere 4/5 Ubers, however, even if a metagame with them allowed had them balancing each other out and somehow made a more balanced metagame as a whole than the final GSC OU, people were already used to "standard" pokémon such as Gengar, Starmie and Snorlax. I'm not saying people were "afraid" of change, on the contrary; when people had 2 absurd pokémon back then, and then Game Freak creates other 2/3 who just look like the first 2, how would they react? "Holy shit just ban them already". It's the most sensible reaction possible. RSE went and repeated it again, this time adding enough, say, "Mewtwo-looking" pokémon to make Ubers a playable (but not balanced) metagame, which got all banned. Game Freak pretty much imposed this "standard metagame" we have right now creating Mewtwo and Mew back in 1995.
But it doesn't mean this "standard" we have right now is bad, nor it means it's good. It's just what it is. Ubers without Kyogre could actually be balanced, but then we have to consider if a (balanced!) metagame with Mewtwo, Garchomp, Wobbuffet, Blissey, Deoxys, etc would be preferable to one with Zapdos, Tyranitar, Starmie, Infernape, Blissey (fuck her), etc. Tangerine raised a vital question on this matter. What would be a "good" metagame? To me, a good metagame would be one that is based on long-time definitions of "standard", but even then is "open" enough to let the lesser ones from the Uber tier to be tested and such, as long as they don't mutate the OU tier enough for it to look like "broken", "Uber-lite", or in better words, a lookalike of what we never wanted the standard metagame to be.
Out of this definition, the "long-time definitions" part is the easiest to define; I already explained it, it's the idea of Standard being comprised of pokémon not "clearly broken" like Mewtwo, which means the 670+ BST crowd except for Slaking and Regigigas and a few Deoxys formes. The "lesser ones from Uber" is a bit deceiving: It's pretty obvious Manaphy, Deoxys-D and Wynaut suck in Ubers. We could even say they are "a step below", and that they deserve being tested more than, say, Ho-oh. But I'm not talking only about them. I'm talking about every pokémon that's the opposite to Mewtwo. If Mewtwo is the essence of unbalance, if a pokémon like him is at the heart of the Uber tier/metagame for the players, then the only kind of pokémon which has a right to even see the light of Standard would be... pokémon that are not "clearly broken" by themselves.
Who would they be?
Well, Gen IV has given us insight onto it already.
Our current Suspects.
Just look at them. "Hey, almost all of them have BST 600". Yeah, but that's not the point. They are the ones the Pokémon community (and I'm taking other forums, sites, etc etc into account) have never universally rejected, and never will. Just go and ask anyone, from the best player of Smogon to GGFan, passing by the Youtube players and the Serebiiforums members. People will disagree about Blissey, Garchomp, Salamence, Jirachi, Wobbuffet. One thinks X and other thinks Y and they will always discuss back and forth about it, while on the other side of the coin, none of them go on Stark Mountain or Policy Review and wholeheartedly say "hey guys we should test Mewtwo for this this and that". Why don't they? Because no one finds sincere arguments to unban/test Mewtwo and his gang. It's ingrained on everybody, they're the pokémon that cannot be unbanned. They are Uber, they forever will be Uber. The lesser ones, like our Suspects, might be strong but maybe, just maybe, they may become part of the Standard metagame as long as they prove themselves to be "tame".
The Latis are an example. Were they Uber in ADV? Yes they were. Were they Uber in DPPt? Seems so. But are they "forever Uber"? No they aren't. They are not tied to a stat spread, an ability, a movepool that forever will be their bane from OU. What would be of them in DPPt had Draco Meteor not been created? The community would have welcomed them with open arms and a party. Deoxys-A would be welcomed with torches and forks and then would tentacle rape everybody.
What do I mean with all that? What am I trying to make? Well, my proposal here is that, for 5th Gen, we treat all Suspect pokémon as Suspects once again, with the same treatment being given to pokémon that are like them. This means that, unless some revolutionary change occurs (like Outrage getting a 70% flinch rate), Wobbuffet, Salamence, Latias, Latios, Deoxys-S, Garchomp, Manaphy and Shaymin-S should be allowed on Gen V at first, and also Wynaut, Deoxys-D and any new or old pokémon that isn't "clearly broken". We'd begin with Stage 3 and already having to deal with shit exploding everywhere (OU or not, those are all ridiculous powerhouses which would surely be top-tier), but I believe it's best to start this way and keeping an eye on all of them then having them all banned based on a DPPt mindset only to begin testing them two years later. Now, what would be of the Uber tier? At first, it would be comprised of the "clearly broken" pokémon. And who would be they? Unless something revolutionary happens (like Air Lock becoming Slow Start), they are Mewtwo, Mew, Lugia, Ho-oh, Kyogre, Groudon, Rayquaza, Deoxys-A, Deoxys-N, Dialga, Palkia, Giratina-A, Giratina-O, Darkrai and Arceus. You know, the "big, badass guys". There seems to be one exception to this, though.
Before I talk about it, I have to bring Deoxys-S to the table, as he's quite the interesting case. He came up two generations later, but is as controversial as Mew. While people thought he was "the king of mediocre" in early DPPt, he got booted one week after Stage 3 started because he was so "clearly broken" people shouldn't even bother with him. He then became a pretty cool pokémon in Ubers as people finally realized how good of a lead he was. However, his Uber status isn't fully ingrained on the community. Deoxys-S was broken essentially due to its 180 Base Speed and access to Taunt and pretty much every good support move except Encore, but even so there were (are?) people who thought it wasn't broken with this killer combo. It's clear to most people that he is broken in DPPt, but there aren't any guarantees he will be next time. You see where I'm getting at? While we may say Kyogre could be OU if Drizzle became Storm Drain, we know it won't happen. But it's possible Shadow Tag is nerfed and Wobbuffet then becomes OU. Deoxys-S won't lose its movepool, neither its Speed, but they might get nerfed somehow with any programming or metagame changes Game Freak adds. ADV Deoxys would be even less awesome if Choice Scarf existed, and DPPt Deoxys would have big problems were Taunt still its ADV self. This is what differentiate Suspects from "true Ubers" in a generation transition. Mewtwo never changes, because it's not on Game Freak's interests to change him. Deoxys-S does because he isn't as "important" as Mewtwo, and is dependent of so many things it's not even funny.
Now on the exception: it's Mew, as I've noticed some people have a suspicion on him since ADV; even being one of the original Ubers, Mew was banned more for its gargantuan movepool back in RBY, a generation where most pokémon didn't have that big of a movepool (or even a movepool at all), than for "the whole picture" like Mewtwo. The gens passed by and Mew's movepool only increased, culminating on the absurd of Gen IV, with him learning all 100 TMs/HMs, almost every Move Tutor and also all +2 stat moves, plus Baton Pass and also Aura Sphere. He's a much more complicated case as we've never let him be tested; since the beginning, he is bonded with Mewtwo. In DPPt, we live in a world where Tyranitar is the elite and Psychic-types are peasants since French Revolution, but even then there's opposition for testing Mew, as opposite to Deoxys-S, his Uber status is too much ingrained on people. Curiously enough, Celebi was (apparently) Uber when introduced in GSC but then came down a generation later (even though many people still considered him Uber) and established himself as an OU pokémon in DPPt. This shows things turned out pretty bad for Celebi for the span of the generations, even if he was introduced as the "GSC Mew". Every "new Mew" (Celebi, Jirachi, Manaphy, Shaymin) was incredibly powerful when introduced and in the following generations but even then, had a chance. The only one who didn't - and still doesn't - is the original Mew, because Mew has this gimmick where he always has to "learn everything" to be the true jack of all trades, master of none.
In a metagame where it's most interesting to be specialized on something rather than a jack, Mew might deserve the same chance his siblings have. We could say Darkrai is on the same boat, but then there's Dark Void, Nasty Plot, Bad Dreams and the stats to pull it all off. He's just right on what he had to have. Mew has "awesome" stats, but nothing specially designated for X or Y, and its main appeal is unpredictability, which may or may not be its "broken point". Gengar is unpredictable because you will not be sure which moves he's running, but once you find one move, it loses efficiency because by then there will surely be something to counter/check/stop it; Salamence is much less unpredictable but its two main sets fuck up everything together and are specially efficient because they're so good on their own they end up used with the same frequency, which means in the end Salamence is unpredictable because you can't know which of the two sets he's going with and when you do, you see it's still absurdly effective and you might have lost something already. Where would Mew be situated? Gengar tier? Mence tier? Even higher than Mence as to ensure he would come down along with the other Suspects only to be booted one week later?
Regardless of the never-ending debate on Mew, I hope that, with the Smogon Council finally rolling and this shenlong-winded post, people will consider starting Gen V as "fresh" as possible, only holding up on the "true Ubers" and letting all Suspects and below (and maybe Mew?) roam free. Any "clearly broken" pokémon will be able to get hooked earlier thanks to the Council, and anything else will have the chance to prove themselves "worthy of OU status" this time around.