Again, to be frank about this, UU is simply at its best right now. It's got a wide variety of abusable sweepers, its fair share of defensive tanks, and enough of the other elements to keep each individual match interesting.
The reason UU is interesting is because Gen V OU is so broken people are only willing to use some Pokes and let others drop all too willingly. And UU's "balancedness" is starting to corrode as a result.
Going back on past bans, such as unbanning Hail, Sun, and Sand, will lead to a rapid centralization of the metagame, much like what happened in OverUsed when Black and White initially came out.
It would also lead to the metagame being more dynamic, in a way. Whether these dynamics actually help the tier any is what would be debated, and I agree that releasing the permanent weather will just wind up being a mixed bag again.
Those weather effects absolutely require you build your team to beat them, which leaves some teambuilding aspects, such as the more frail sweepers - Weavile, Honchkrow, Azelf, and others like them - off the table as they cannot afford to be taking the passive damage brought by Hail or Sand.
This I can agree with. Some sweepers despise residual damage from Hail or Sand, thereby making those weathers somewhat annoying. However, balanced metagames in the past have had permanent sand before. Two previous generations' worth of it, to be exact.
Sun on its own is extremely unhealthy without a permanent way of setting Rain up in the lower tiers, as the number of Chlorophyll users and overpowered Fire-types this side of BL gives it way too much to work with. The likes of Shiftry, Sawsbuck, Victini, Darmanitan, and Victreebel would quickly snap the metagame in half, which really isn't worth it.
While this is agreed upon, you also forget some tanks, such as Cresselia and Umbreon, have their reliable recovery being stronger in the Sun on top of all that. I might have to make a defensive Sun team as part of my next Dark Horse Project in OU to destroy this perception of "it only benefits hyper offense" using Hope.
Hail, I'll admit, isn't to be as feared as it once was. Mamoswine and Kyurem were what made it so dangerous, and with them out of the picture, won't be as much of a problem. However, unbanning hail will lead to an onslaught of "you banned Snover, so why not ban Hippopotas or Vulpix" discussions and other false sympathies towards the weather starters.
As much as I want eternal winter to cover all the Gen V tiers, I'm going to agree that releasing Hail would set a garbage precedent; in the case, it would deliver chicanery in the other weather NFEs being released.
Sand, we all know will be a bugger to handle, as things like Sandslash, Stoutland, Cacturne, Gligar, and Rhyperior all of a sudden become extraordinarily difficult to handle while retaining momentum for your team.
Gligar is no longer a problem, neither is Cacturne. Unless you mean Immunity Gligar and Water Absorb Cacturne making teambuilding still more difficult to counter stuff reliably, then of course. As for Sandslash, Stoutland, and Rhyperior, though - you'd be right in that regard.
Weather is unhealthy in this tier, no matter how you look at it. My question to those asking for weather to be retested, is why do you want to disrupt the tier so badly? If you want to play an organised tier, play OU, but don't come around asking for the same styles of play in a completely different tier.
While I don't agree with the attitude, I can agree that UU is slightly better without permanent weather in it.
There's a reason as to why BW2 UU is so comparable to DPP OU, and I'd like to see it stay that way.
The irony in this statement is that permanent Sand and permanent Hail were allowed in DPP OU. There are also several contrasts, mainly in part to how a majority of the DPP OU Pokemon aren't actually in B2W2 UU. I'd like to see something like Infernape drop to UU before the comparisons start, for example.
However, UU is a much more comfortable tier for me to play in compared to the likes of OU and RU. Please don't free anything, as there is still some banning to do before the tier is perfect.