My team for 3v3 battles online, will probably be something like:
Blastoise- holding Megastone
Moves: Depending on what's affected by its mega launcher ability, it'll probably go something like this:
-Water pulse (depending on how much more powerful mega launcher makes it) unless its still weaker than surf, in which case I'll opt for surf
-Ice beam (coverage)
-Focus blast (I believe it also gets a boost from mega launcher, also for coverage)
-Water spout (Super accurate although health dependant move)
Description: Blastoise's mega form will be the main focus of the team, once set up, with its great defence and extremely powerful upgraded special attack it will be able to shrug off most priority moves like extreme speed while dishing out tremendous damage with water spout, once under a certain HP thresh-hold surf becomes a more powerful and just as accurate option
Politoed- Holding Choice Scarf, Ability: Drizzle
Moves: A standard suicide lead Politoed, unless theres a Ninetails or possible mega Charizard Y on the opposing team, then try to keep this alive as long as possible.
-Hydro pump
-Ice beam
-Focus blast
-Toxic (a just in case move, to outlast opposing weather users)
Jolteon- Holding Shuca Berry (Halves a supper effective ground type moves damage) Abillity: Volt absorb
Moves: Jolteon is the one to set up Blastoise, strategy explained below
-Agility
-Baton pass
-Thunder
-Toxic/Detect (whichever you would prefer)
Strategy: So I've been testing this on PO with a placeholder MegaBlastoise (A normal Blastoise with choice specs to somewhat emulate the boosted SpA, it isnt as good as the real deal though it still does amazing, which goes to show this monsters true potential.) You start by sending in Politoed, to activate drizzle, now theres two choices: If the enemy doesn't appear to have a weather starter on their team than go with a suicide hydro pump. If they do look like they have one, KEEP POLITOED ALIVE, once rain is properly up switch to Jolteon, now Jolteon has the best synergy with this team for two reasons: if you predict something to hit Politoed or Blastoise with an electric move, or paralysis, you can switch to Jolteon to absorb it and heal its health, the other reason is that Jolteon attracts earthquake users like moth's to a flame, we're counting on this, Use agility and tank an earthquake with the Shuca berry, one agility is usually enough to make blastoise faster than most threats, so on the second turn baton pass, one of two things will usually happen: The opponent will predict your Pass and switch to something else, OR they will attempt to EQ you again, either one is favourable as now you have your Blastoise on the field, Mega evolve and waterspout to victory!