Single Set Format Concept - FST Accelgor

Based off NoGoodName's idea - rules being the deck must be made entirely from a given set, and no Rule Box Pokemon.

Since there is no way Meloetta would ever be legal in a slow format like this, I used the next best thing- Accelgor.

Deoxys gets a lot more support as an archetype due to having Chili/Cilan/Cress, Fusion Strike Energy and Elesa's Sparkle, but Accelgor has extremely good synergy with Skater's Park and Cross Switcher. This allows him to do 120 damage for just one Grass energy.

Minun and

Based off NoGoodName's idea - rules being the deck must be made entirely from a given set, and no Rule Box Pokemon.

Since there is no way Meloetta would ever be legal in a slow format like this, I used the next best thing- Accelgor.

Deoxys gets a lot more support as an archetype due to having Chili/Cilan/Cress, Fusion Strike Energy and Elesa's Sparkle, but Accelgor has extremely good synergy with Skater's Park and Cross Switcher. This allows him to do 120 damage for just one Grass energy.

Minun and Plusle are a nice package inclusion in this deck (and any FST deck in this theoretical format). Minun has a Call for Family move, allowing you to set up your board quickly in conjunction with Battle VIP Pass, and Plusle can follow up with a 120 damage move for one energy.

Jynx is simply for draw support, and Snorlax is a meh-ish Basic backup attacker that is the best I could find (consider Durant FST here if you want to improve your matchup against fire decks)

FST's items are all extremely strong. Battle VIP Pass for turn one Pokemon search (with Chili, Cilan and Cress as backup for Accelgor only), 4 Cross Switcher for gust plays, and 4 Crossceiver for Pokemon recovery. Cram-o-Matic is an absurdly strong inclusion, allowing you to search for Dancer turn 1 for a six-card draw. Skyla and the Schoolboys/Schoolgirls are the main package of draw support. 

Finally, Skaters Park allows you to chain Accelgors and two-shot probably anything, barring resistances and damage reduction.