As far as Sleep Clause vs No Sleep Clause goes, I would personally prefer no sleep clause, as Smeragle's Dark Void can be countered effectively while maintaining team synergy. (I have an example team I can post if needed). A Taunt/Safeguard user with Lum/Chesto Berry can save a team from Smeargle if used correctly. The Freeze and Evasion clauses are not as big of a problem in my opinion.
On another note, you cannot have Scarf Jirachi and Scarf Smeargle on the same team if Item Clause is in effect.
I would like to see:
6v6 Double Battles
No Sleep Clause (Arguable)
No Evasion Clause
No Freeze Clause
Species Clause
Item Clause
If an attack knocks out both players’ last Pokémon, the player that used the attack loses the match. (Explosion, Selfdestruct, Double-Edge, Volt Tackle, Flare Blitz, Take Down, Submission, Brave Bird, Wood Hammer, Head Smash, Struggle, Perish Song, and Destiny Bond, Life Orb)
If an environmental effect knocks out both players’ last Pokémon, the result of the match is a tie (Hail, Sandstorm, or Sunny Day)
If all remaining Pokémon are knocked out due to Stealth Rock or Spikes, the result of the match is a tie.
If a Pokémon’s ability or held item results in all remaining Pokémon being knocked out, the result of the match is a tie.(Aftermath, Liquid Ooze, Rough Skin, Jaboca Berry, and Sticky Barb)
This would be the banlist/Uber List:
Mewtwo
Mew
Lugia
Ho-Oh
Celebi
Kyogre
Groudon
Rayquaza
Jirachi
Deoxys (All Formes)
Dialga
Palkia
Giratina (All Formes)
Phione
Manaphy
Darkrai
Shaymin (All Formes)
Control over nicknames is also something to consider, although it is very trivial.