Doorknob, I suggest you look at the arena I have come up with before committing to reffing the battle. I don't want you to get too frustrated by reffing a battle with such a complex arena. If you are still willing to ref it, though, then I will send in my team shortly.
See that phrase "I'll just leave the arena up to the ref"? That's my cue to say "I'll take this! Editing in arena shortly."
And here is that arena:
The battle takes place on a huge wooden airship that’s currently high up in the sky. As such, there is no external water source. There are piles of cannonballs in the corners of the arena that can be used as rocks for moves like Rock Slide; however, there is no grass for moves like Grass Knot.
At the end of every round, a Bullet Bill will be fired at each pokemon (including ones that have just been KO’d). The Bullet Bills will hit during the following round on action 1 or 2 (a 50:50 chance of each for each Bullet Bill) at priority -0.5. Once it hits, a Bullet Bill explodes (treat this as a 20 BAP physical normal-type attack from rank 5 attack) and is gone for good. However, the following countermeasures exist:
If the pokemon being targeted by a Bullet Bill uses Dig, Dive, Bounce, Fly, Shadow Force, Sky Drop, evasive Agility, Teleport or the Dodge command on that action (including any sustained evasive actions for those moves that get them), or if another pokemon uses Sky Drop on that pokemon in that action, the Bullet Bill will miss completely and fly off into the night.
Any pokemon can destroy any Bullet Bill by targeting it with an attack or attacks that do at least 15 damage to it (treat the Bullet Bill as a Steel-type with rank 3 in both defensive stats and the abilities Clear Body and Levitate); however, if the move that destroys a Bullet Bill is a contact move not named U-Turn, the pokemon that used that attack will take half the normal Bullet Bill damage (that is, half the actual damage, not half the BAP). Also, all attacks that target the Bullet Bill cannot hit anyone else, even if they would normally hit multiple targets.
The moves Sky Drop, Seismic Toss, Circle Throw, Vital Throw and Storm Throw can be used on any action to redirect one and only one Bullet Bill to an opponent as long as the pokemon using the move can use it on a pokemon with a weight class of 5. The ability Rebound can also do this, but only on the action when the Bullet Bill would normally hit, and the weight class restriction does not apply in this case. In all cases, a move that redirects a Bullet Bill does no damage to it. The redirected Bullet Bill will hit its new target on the action after it was redirected, which may be action 1 of the following round. Each Bullet Bill may only be redirected once.
Protect and Detect do protect the pokemon from Bullet Bill damage, but this damage is still factored into the energy cost of the move.
If a pokemon has a Substitute up when it is hit by one or more Bullet Bills, the Substitute blocks the damage from one Bullet Bill only, and the Bullet Bill destroys the Substitute regardless of how much damage it would normally do to the pokemon.
If a round ends early for any reason, any pokemon who still haven’t dealt with the Bullet Bills heading towards them automatically use the Dodge command once to dodge them all (and pay the full energy cost). If a pokemon does not have enough energy to use the Dodge command, it doesn’t bother and instead gets hit by the Bullet Bills as normal.