I think the simplest gimmick you can pull off involves mind games.
When you look at a team, you can guess which Pokemon is going Mega in a "normal/standard" battle. So use that kind of guess against the opponent! Load up your team with 6 Pokemon whose Megas are ALL threatening, and make the opponent keep guessing which guy is going Mega. THEN the real mind games can start. Such as... do you even HAVE a Mega Stone attached to anyone?
A team composed of: Beedrill, Salamence, Garchomp, Tyranitar, Charizard, and Blaziken, for example. "Oh, the Beedrill is DEFINITELY going Mega." Nope! Charizard goes Mega and Blaziken suddenly gets Sun boosted Flare Blitz.