Ended up with a 1622 rating after 26 battles. Don't have too much time left so I think I'm going to stop here. My team was:
Magikarp@Mystic Water
Ability: Swift Swim
Nature: Modest (+SpA -Atk)
EVs: 252 SpA, 204 HP, 36 SpD, 12 Spe, 4 Def
-Hydro Pump
-Bounce
-Flail
-Splash
Debate the item for a while. I thought about going with Eviolite but decided I wanted more offense. I didn't want to be locked into a move, so Scarf and Specs were both out, and something else on my team was already using Life Orb, so I went with Mystic Water to give Hydro Pump a little more power, allowing me to secure 2HKOs on other Magikarp without Eviolite or significant Special Defense investment. The Speed EVs are not only to outspeed other Magikarp with no Speed investment, but also actually because I wanted it to outspeed my own Blaziken on turn 1.
Clefable@Absorb Bulb
Ability: Unaware
Nature: Modest (+SpA -Atk)
EVs: 252 HP, 156 SpA, 60 Def, 36 SpD, 4 Spe
-Moonblast
-Fire Blast
-Meteor Beam
-Protect
I didn't use it too much, but it did help against a couple Dragapults.
Blaziken@Weakness Policy
Ability: Speed Boost
Nature: Adamant (+Atk -SpA)
EVs: 252 HP, 156 Atk, 60 Def, 36 SpD, 4 Spe
-Flare Blitz
-Close Combat
-Stone Edge
-Detect
One of the MVPs on my team. Decided to go for a more bulky spread, which most people did not expect. The downside was that I often needed more than one Speed Boost to outspeed certain Pokemon, but I was usually able to work around that. It's also weak to both Hydro Pump and Bounce, making it easy to have my opponent activate the WP.
Durant@Occa Berry
Ability: Hustle
Nature: Jolly (+Spe -SpA)
EVs: 204 Spe, 252 Atk, 52 HP
-X-Scissor
-Iron Head
-Stone Edge
-Protect
Only used it a couple times, but it worked out well those times. Went back and forth on the item, but ultimately decided to go with Occa Berry to give me a chance against Fire-types. Never ended up using the berry at all.
Cradily@Custap Berry
Ability: Storm Drain
Nature: Calm (+SpD -Atk)
EVs: 252 HP, 124 Def, 100 SpD, 28 Spe, 4 SpA
-Giga Drain
-Meteor Beam
-Earth Power
-Recover
Pretty standard Cradily, with a small amount of Speed investment to help deal with other Cradily. I only used it twice, but it held its own both times.
Rotom-Wash@Life Orb
Ability: Levitate
Nature: Modest (+SpA -Atk)
EVs: 252 SpA, 164 Spe, 92 HP
-Thunder
-Hydro Pump
-Dark Pulse
-Hyper Voice
Another MVP of my team. I was originally going to use Barraskewda as my sixth, but made a list-minute swap to Wash Rotom after realizing how thoroughly it destroys Lapras. Definitely an underrated Pokemon here. I used it quite often, and I don't think many of my opponents expected it. Though it has a poor match-up vs. most Grass-types, there are lots of things it beats that you might not expect it to. Was even able to take down a Porygon2 with it. I do regret not carrying Protect though--I thought it would be a good idea to have access to Max Strike, but in practice I didn't ever use it, and there were a couple times where I lost but could've saved myself with Protect/Max Guard.
Overall Blaziken and Rotom were my MVPs, but I used everything on my team at least a couple times. Competition was super fun, really hope to see more silly competitions like this.