The midfielder is the only “U.A.” monster that you can Normal Summon without Tributing, so it’s a very important card. Ideally, you would open with it in your starting hand, but you can always draw it via Draw Sense: Low Level. Normal Summon Midfielder and then switch him out for a Level 5 or higher “U.A.” monster-like U.A. Mighty Slugger or Perfect Ace.
Midfielder’s secondary effect allows you to return another face-up “U.A.” monster to your hand to Special Summon a “U.A.” monster with a different name from your hand. This effect can be used to get around the “once per turn” restriction all “U.A.” monsters have on their primary effect or to simply prevent them from being destroyed by a card like Treacherous Trap Hole.
When Mighty Slugger declares an attack, your opponent cannot activate cards or effects until the end of the Damage Step. You can use this effect to temporarily disable your opponent’s backrow or to prevent your opponent from negating a Spell/Trap Card using Legendary Six Samurai - Shi En’s effect.
Mighty Slugger is a Level 5 monster, which means it can be Special Summoned from the hand or Graveyard via Feast of the Wild LV5 together with a U.A. Perfect Ace or another copy of Mighty Slugger. Feast of the Wild LV5 does negate the effects of the monsters it Special Summons, but you can still return them to the hand using another “U.A.” monster in your hand and then Special Summon them back to the field.
Rival Rebounder’s secondary effect allows you to Special Summon another “U.A.” monster from your hand or Graveyard when he is Special Summoned during the opponent’s turn or Normal Summoned. Special Summon The Tricky by discarding U.A. Penalty Box or a “U.A.” monster you want to Special Summon, and then Tribute it to Summon Rival Rebounder.
Cosmic Cyclone can be used to get rid of your opponent’s back row or to disrupt their plays, but it also allows you to activate your Skill, giving you access to U.A. Midfielder. Set Cosmic Cyclone, banish Geartown, Ancient Gear Fortress, or Shien's Dojo, preventing your opponent from Summoning problematic monsters.
U.A. Stadium is the Field Spell of the archetype and it has two effects: one that activates if a “U.A.” monster is Normal Summoned and one that activates if a “U.A.” monster is Special Summoned.
If a "U.A." monster is Normal Summoned to your side of the field: You can add 1 "U.A." monster from your Deck to your hand.
You can Normal Summon U.A. Midfielder or Tribute Summon for any of your higher-level monsters and get a monster to tag them out for right away.
Once per turn, if a "U.A." monster(s) is Special Summoned to your side of the field: All monsters you currently control gain 500 ATK (even if this card leaves the field).
Not only the ATK boost stays even if the card is banished by a Cosmic Cyclone or destroyed, but it’s also permanent as long as that monster stays face-up on the field. Use the ATK boost from U.A. Stadium together with Beatdown to quickly overwhelm your opponent.
A Continuous Trap Card that banishes a monster that battles with a “U.A.” monster at the start of the Damage Step. Sounds familiar?
Penalty Box, unfortunately, cannot Special monsters from the hand and its banishing effect lasts only until the 2nd End Phase of the opponent, but, if it ends up in the Graveyard, you can banish it to add a “U.A.” Spell/Trap Card to your hand (Stadium). The fact that you can banish Penalty Box from the Graveyard means that you’re free to run Treacherous Trap Hole in this Deck.
Draw Sense: Low Level Can be used each time your Life Points decrease by 1000. In the Draw Phase, instead of conducting a normal draw, draw a random monster of Level 4 or lower.
Use Cosmic Cyclone to lower your Life Points and draw U.A. Midfielder. Even though you can use The Tricky, Dynatherium, Mithra the Thunder Vassal, Paleozoic Canadia, and even Feast of the Wild LV5 to get your Level 5 or higher “U.A.” monster out, Midfielder is still your primary way of Summoning them (and also the one that takes fewer resources).
[Skill] description (After Aug 29)
Beatdown! This turn, the Atk of all Level 5 or higher face-up monsters on your field increases by the number of monsters of Level 5 or higher on your field times 300.
Beatdown works particularly well with U.A. Mighty Slugger, which is the main monster you are going to use to attack, but it also makes Perfect Ace offensively more relevant.
If a “U.A.” monster is flipped face-down by a Paleozoic Canadia or a Floodgate Trap Hole, you can return it to your hand to Special Summon another one. Generally, it’s very easy to disrupt your plays, especially early on.
Running a lot of high-Level monsters is always a risk: you might find yourself with an unplayable hand. This might change if U.A. Signing Deal is released.
U.A. is the type of Deck that takes a few turns to properly get going. It would be very easy for an aggressive Deck to take advantage of these weaknesses and OTK you on Turn 2.
If you Special Summon Perfect Ace and Mighty Slugger via Feast of the Wild LV5, you need a monster to switch them out for. If you don’t have another “U.A.” monster in your hand, the ones on the field are pretty much just beat sticks that can’t even attack.
With Perfect Ace and Blockbacker, this deck is even stronger than Six Samurais in terms of negating. The only difference is 6sam has pot of greed while this deck pretty much bricks if you don't have midfielder in you starting hand.
There's really only three ways they can "handle" an overpowered deck.
1: Powercreep it into irrelevance, which makes the game increasingly less balanced.
2: Nerf it, allowing existing decks and new decks to compete with it.
3: Do nothing, and never release anything stronger, making the game stale very quickly.
This deck is either really good or really bad depending on your opening hand. If you don't start with Midfielder or something that's gonna survive turn #1, your screwed. Otherwise, Stadium + Penalty Box can work wonders with removing things you don't want to deal with. If they eventually add more spell/trap support for this archetype, it could see some more playability