Ok.. correct me if i'm wrong, but this thread was to annihilate the most invaluable character to the story, so that this party would just... die right? =X

If that's the case.. I'd say take Rikku out of the equation.. sure her dmg wasn't anything exceptional unless you wanted to go out of the way to train her (like i did.. and now i'm reaping the rewards of a fast efficient fighter xD ) but on her own.. she could mostly be considered the Toolbox character, capable of doing almost anything at the start.

Take for example her overdrive.. Nothing and seriously nothing can match hers in the early parts of the game. . Throw 2 maps together, and you blast the opposition to smitts with 2k dmg.. closest thing to that would be Yuna's grand summon, just that rikku has a lower cooldown.. need healing, just use one of her potions combi..

She's also useful for a backup elementalist (thats if you've been stealing on a regular basis) when Lulu just isn't enough (mana runs out prematurely.. stuck down by a chunk of meanies etc) just dun fear to spam those dmg items today.. (you hardly use them anyway i'm sure xD )
anyways.. what would you do if Rikku nv came in, and helped out with your customize weapons/armour option?

Anyways.. if you're talking about taking the worst char out.. i'd say Wakka.. his style nv suited my playing, and he's hard to train without blitzball.. useful at certain times early on.. but not really needed..