Mega Garchomp seems a fairly strong contender and so does mega Khangaskan. But the most important thing about Mega pokémon is they're switching into an attack at a time when they most likely have yet to mega evolve. Gyarados and Mawile have Intimidate to help them on the switch in, but Mawile's too slow to be useful. While I wouldn't bet the incoming attack will outright kill them, it could weaken them to the point where the odd priority move ends your sweep. Lucario resists Scizor's bullet punch and has his own to deal with Breloom and Azumaril, but no real answer to Talonflame. Gyarados also resists the bullet punch and aqua jet on top of his intimidate. So Lucario and Gyarados are my recommendations.I was wondering which Mega would profit most from a BP Scoli (+2At +1 Sp).
Mega Heracross came to my mind, however it has the disadvantage of sharing bug types so BP might swap it into certain death.
Mega Tyranitar or Mega Gyrados both have some solid bulk (so does chomp) to survive a swap.
Gyra comes in with Intimidate which is a huge plus since it might force a switch, however Tyranitar surves basically and special attack which isn't focus blast.
Absol also COULD be a solid choice - it's fragile, but if it really does get the setup sponsored it's not stopable by and status-move-prankster-guys anymore (only by a strong mach-punch user).
If you go with Gyarados, I'd recommend trying out an assault vest pokémon as a second baton passing choice. That way you have a switch in for both special and physical attacks.