Then I will lead with Marowak (sorry, it's just good business). I'm going to assume that you will use earthquake, since substitue will just leave you with less health, and leave you more vulnerable to Marowak's attacks, and you have nothing else to affect him. Marowak, with maxed def. takes the hit with relatively low damage, responding with an earthquake of his own, potentially one-shoting Electivire. You then send out Dragonite, using the original pseudo-legendary to take Marowak out for the count with Outrage. I send Lapras out. You either continue with Outrage, or get confused, but I'll assume it hits, but it takes only 1/4 of Lapras's HP. Lapras then one-shots Dragonite with Ice Beam. You then send Gengar to put Lapras to sleep, use Nightmare, and then finish it with dreameater. I send out Umbreon, and use faint attack, and if that doesn't one-shot Gengar, I will use Psychic to end it, since you dare not use hypnosis if we include special abilities in this (because Umbreon has Synchronize). You then send out Volcarona to use bug buzz, taking out Umbreon. So I send in Electabuzz and use thunderwave to slow Volcarona down, and then I will use thunder to take care of it. Last, you send out Registeel, who takes a Cross Chop, losing at least half his health. He earthquakes Electabuzz, taking out the rest of his HP. I send out Typhlosion, who uses flamethrower to take the rest of registeel's health.
It would be a tough battle, but I think, ultimately, I'd win out.