If a Pokemon is OU, there can be no debate as to whether it is allowed in UU.
Does it really have to be?
Suppose that Nidoqueen is used so much that it rises to OU. But we see that Nidoqueen doesn't break the UU metagame at all. So why does Nidoqueen be banned?
I know there are a lot of people calling for the OU Metagame to be more diversified - even to the point where people are trying to consider banning Stealth Rock.
So why must we ban Pokemon just because of usage?
I was under the impression that Pokemon tiers were based on usage simply because usage gives a pretty decent degree to how useful a pokemon and thus "how powerful it is".
I simply disagree with the tiers being based sheerly on usage. If we are going for balanced and varied metagames we should simply take into account whether or not a Pokemon is overpowering (see definition in "What is Ubers" thread) not how much it is used in the other metagames. This may actually limits what is possible in the lower tiers without real solid definition at all other than what seems to be an arbitrary cut off.
To illustrate my point, I will use this example. Suppose that we base OU simply on usage based on Ubers. The top 75% of Ubers metagame is then banned from being OU. Blissey and Metagross are now gone, despite that most people find them perfectly fine in OU. And now, because Blissey is gone, we find that special attackers simply rip through the game.
Yes, I know that OU is simply meant to be a balanced metagame, but this example illustrates my point (or "suspicions" but I do believe that it isn't baseless at all) But the thing is we can balance the lower tiers better simply by allowing "OU lites"(NFEs like gligar) and unbanning Pokemon that may not overpower the game.
Tiering would be improved significantly IMO if Smogon was more liberal in the bannings/unbannings in order to experiment. It will take forever for a numerical cutoff for "overcentralizing" to be available if this isn't done. Pokemon is about statistics - and if this definition applies even onto the Pokemon metagame then it's time that people actually try to put some tests to the data and try to figure out exactly what causes what rather than try to just say "usage" determines everything because it just feels completely arbitrary.
If you want Pokemon to be a much better competitive game, I recommend you all work for it by being a bit more competitive.