I want to have an option in Linked Battles for the following:
Single Battle
Set level up to 50. Special Pokemon allowed. Up to 3 Pokemon allowed. Duplicate Pokemon/Items not allowed.
If you're playing on the 3DS, Free Battles with Restricted Pokémon allowed is going to let you do 3v3 at level 50 with all mons in the game.
source (and a good place to ask any more Battle Spot questions)