Which Pokemon will be banned to Ubers?
Raffiti - whoever thought giving Smeragle actual stats was a good idea could very well be in contention for a Darwin award. This thing is absurdly versatile, it can do literally anything, and with offensive stats of 80/80/90, it can very feasibly run a Shell Smash set with the help of Spore. After Shell Smashing, Raffiti can proceed to sweep the opposition with it's perfect super-effective coverage in the form of Expunge + Flamethrower/Fire Blast. Due to it's power, versatility, and access to Nuclear type moves without facing the drawback of actually being a Nuclear type, Raffiti is the most broken mon in Uranium and needs to be banned.
Urayne (alpha) - no reason to talk about the beta form when the alpha one is already broken. Over base 100 Speed and over base 130 Special Attack allows this thing to hit hard and sweep teams without the need for a choice item. While not Nucleon's Hyper Voice, Radioacid still has a BP of 370 against 90% of the game and Urayne also has access to Fire Blast, giving it perfect super effective coverage. It even gets access to Nasty Plot, allowing it to smash through stall teams with ease.
Nucleon - still broken, but it takes a backseat to Raffiti and Urayne in my opinion. While Nucleon's Hyper Voice hits faster and harder than any of Urayne or Raffiti's options and Nucleon doesn't require any turns of setup to reach it's gamebreaking levels of power, Nucleon pales in comparison to Urayne and Raffiti due to it's linearity. Nucleon will almost always be running Scarf, meaning that simply switching into a Steel will get the job done most of the time. This doesn't mean that Nucleon isn't broken, not by any stretch of the imagination. The centralizing effect it has on teambuilding is extremely cancerous, and while it is checked by steels, it can just as easily be used as double switching bait to lure out steel types. Nucleon is extremely unhealthy and needs to go.
Jerbolta-N - The fourth and final mon that should be quickbanned from Uranium OU in my opinion. While Jerbolta-N only has 85 base Special Attack, it makes up for this with it's 110 Base Speed allowing it to outspeed most things, 370 BP Radioacid, Nasty Plot, perfect supereffective coverage with Earth Power, and worst of all, it's ability - Quick Charge. Quick Charge gives Jerbolta the ability to use that 370BP Radioacid as a priority move on the turn it switches in, which is beyond insane. The sheer threat of priority Radioacid allows Jerbolta-N to force switches with ease, set up Nasty Plot on said switches, and proceed to sweep the enemy team with ease thanks to it's perfect super effective coverage mentioned earlier.
The four mons I mentioned above should be quickbanned in my opinion. There are some other mons that I believe should be banned, but a suspect test would be required to justify the banning of these mons. i will list them below:
Inflagetah - Inflagetah's priority attacks deal way too much damage and create an overcentralizing effect on the teambuilding process, as due to Inflag's oversaturation and it's ability to completely dismantle unprepared teams, all teams must be built with a way to deal with Inflag in mind. Unfortunately, mons that can effectively neuter Inflag are few and far between, overall limiting liberties one can take when teambuilding. The best answer to Inflag is Tubareel, and while Tubareel is not a bad mon by any means, using it generally means foregoing use of other useful dark types such as Beliaddon and Oblivicorn, which as mentioned before, limits teambuilding options. Also, it has been recently revealed through data mining that Inflag gets Belly Drum through breeding, which may put Inflag in contention for a quickban.
Archilles - Archilles also gets Belly Drum through breeding. With a base 125 Speed, access to Flare Impact, and impeccable Fire/Ground STAB combination, very little can stop Archilles after it has Belly Drummed. Setting up Belly Drum is not a difficult feat either, as Archilles' aforementioned base 125 speed and Fire/Ground typing make it an excellent revenge killer, which leads to it being very good at forcing switches. To make matters worse, Archilles can firther empower it's Flare Impacts by using Blaze as it's ability and setting up a substitute before Belly Drumming - this will put Archilles into Blaze range and further increase the strength of it's Flare Impacts. This will also mean that Salac Berry will make Belly Drum Archilles even more threatening, should Salac ever be released.
Lanthan - this thing has excellent defensive typing, and 110 / 130 / 109 defenses makes it nearly impossible to oneshot. Lanthan, on the other hand, will have no trouble one shotting your mons thanks to the combination of Subduction/Metal Cruncher + Sheer Force coming off of 106 base Attack. Throw in a Choice Band for the fun of it, since after all, there's no kill like overkill. Slides into teams with ease, is nearly unkillable, and deals way too much damage. I will be very surprised if this thing isn't banned at some point.
Yatagaryu - anyone who plays XY/ORAS OU knows how terrifying Zard Y is. It has an obscene Special Attack stat, and it's Fire Blast gets boosted not only by it's massive Special Attack stat but also by STAB and a sun boost. The only thing holding it in check is the fact that it is a mega, which prohibits it from holding an item, it has a mediocre speed of 100, and it has a 4x weakness to Stealth Rock. Yata is essentially Zard Y except without any of these weaknesses. It has base 120 speed, allowing it to outspeed just about everything, it can hold Life Orb to boost it's attack even further through the roof, it doesn't take up a mega slot, and it takes normal damage from Stealth Rock. As an added bonus, it's Thunder is 100% accurate, it's weather condition deals electric-based Stealth Rock damage between turns, and it even gets Nasty Plot, in case you would rather erase your opponent's mons from existence instead os simply nuking them.
Syrentide-M - personally, I don't actually think Syrentide-M is banworthy, although there are others who would disagree with me. Syrentide is very linear, which, in my opinion, keeps her from being too broken. Considering that doesn't stop Nucleon from being worthy of a quickban, Syrentide's linearity may not be enough to warrant keeping her around. Time will tell...
What are some key powerhouses in OU?
Metalynx - badass steel #1. Excellent defenses, great defensive typing allowing it to take neutral from Ground, and a Mega which allows it to double as an offensive wallbreaker. A staple of the meta for sure, this thing will guarantee Fire types a place in the meta. (see: Ferrothorn)
S51-A - badass steel #2. While it is not quite as defensive of Metalynx (although 105/90/90 defenses are nothing to scoff at), it makes up for this with access to Levitate and Rapid Spin, making it an excellent mon for some teams. It even has a Special Attack of 110 as a bonus. (see: Metagross, Excadrill)
Fafninter - badass dragon #1. Extremely bulky, hard hitting, and versatile, this thing has it all. It can Dragon Dance, it can Bulk Up, it can set up rocks, whatever you need it to do, it can do. It's only issue is it's atrocious typing, which makes it hard to fit on teams. (see: Kyurem-B)
Tracton - badass dragon #2. It's stats aren't as great as Fafninter's, but it's typing is excellent, leaving it open to only two weaknesses. While it is not as versatile as Fafninter, it does it's one job well - sweeping with the combination of swords Dance and Speed Boost. Tracton is a premier sweeper to watch out for in Uranium OU, and it will beat you if you aren't prepared for it. (see: Zard X)
Luxelong - badass dragon #3. Dragon/Fairy is an excellent defensive typing, and one might think to compare Luxelong to Mega Altaria at first, given the similarities of their roles (both are utility focus cleric type mons) and their typing. However, I consider Tornadus-T to be a more apt comparison, and both Luxelong and Torn-T make excellent abusers of the Assault Vest thanks to their Regenerator ability. (see: M-Altaria, Tornadus-T)
Cocancer - badasss ground #1. Grass/Ground may have a nasty 4x weakness to Ice, but this can be easily dealt with by running Steel and Fire-type switchins. Other than the ice weakness, Grass/Ground is an excellent typing, especially so considering just how good Ground is in Uranium. Not only does Cocancer get to join the Ground club, it also gets to become a premier Ground killer thanks to it's Grass typing. Additionally, Cocancer has impeccable defenses (not much is getting through 90/120/115), and is very versatile. it can set up rocks, it has access to Synthesis for self-recovery, it can set up Curse, and it can even sweep teams with Shell Smash. Just as Metalynx has guaranteed fire types a place in the meta, Cocancer has guaranteed Ice-types a place in the meta. Be sure you at least have some Ice coverage or be prepared to face the wrath. (see: Hippowdon, Tangrowth)
Laissure - badass ground #2. One of the few non dual-typed mons in Uranium, Laissure's versatility allows it to do pretty much anything. It can sweep and revenge kill with Moxie and Scarf, it can pivot with Intimidate and Band, and it can set up both rocks and Spikes, making it a premier hazard setter. Definitely a mon to watch out for. (see: Landorus-T)
Beliaddon - badass fire #1. With a base 145 attack, impeccable bulk, typing that is beneficial from both an offensive and defensive standpoint, and two of the best abilities in the game, Intimidate and Defiant, Beliaddon is no joke. Intimidate allows Beliaddon to force out switches like no other, and Defiant allows it to brutally punish your opponent's Defoggers by practically guaranteeing a kill. It can wallbreak with Band, revenge kill with Scarf, you name it. This demon is versatile in addition to being insanely powerful. The best mon in Uranium OU imo (not counting the ones that I think should be banned). (see: Tyranitar)
Chimaconda - badass fire #2. Combine Fire, one of the best offensive typings, and Poison, one of the best defensive typings, and you end up with a monster. Petrify allows Chimaconda to pivot with it's excellent defensive typing (4x resistance to Fairy is pretty great) and revenge kill as well. Contrary lets Chimaconda set up a sweep via Overheat spam. Both are threatening options, and teams that do not adequateply prepare for the chimera through use of Ground types will be punished for doing so. (see: Heatran, Serperior)
Who are the Dedicated Leads to beat?
Laissure and Astronite are probably the best. Already talked about Laissure, Astronite is fast, gets both Taunt and Stealth Rock, and has access to both Sturdy and Expolsion. It also gets both Recover and dual screens, which could very well become a viable option when Light Clay is released.
Which Pokemon will be banned from Little Cup?
No idea. Little Cup is likely something that will be put on the back burner for a long time.
Should we adopt Smogon's rules / clauses?
Of course.
Thoughts on Tandor's Legendaries in competitive battling?
If they aren't overpowered, there is no reason not to allow them. Lanthan and Urayne (and maybe Seikamater) are the only ones that will probably be banned anyways.
With Syrentide-M and Metalynx-M in OU, who are the Wallbreakers to watch out for?
Beliaddon's Infernal Blade can punch through Syrentide-M and Metalynx-M. For those who are unaware, Infernal Blade deals super effective damage to Fairies no matter what, even if they have secondary typing that resists fire (like Syrentide-M for example, it would still take super effective from Infernal Blade despite Water resisting Fire).