I Officially Dub this... the Hardass party.

Seifer (FFVIII)
Squall (FFVIII)
Paine (FFX-2)
Barret (FFVII)
Amarant (FFIX)
Auron (FFX)

I'm assuming that we're keeping the original game rules intact? in that case, Paine can be popped trained as a White Mage, Both Seifer and Squall can Junction magic high to keep everyoine alive, we can pop some Full Cure materia to Barret, and Amarant and Auron both have Self Healing Abilitys. (Chakra...and i forget what aurons was, but i believe he had them.)

Other than that....Everyones dies from ultra barrage of physical attacks. (saving MP to heal up or Summon)