Well, okay then. I guess I can talk about it a little bit more.
The Gullwing girls are fighting some plant creature; nothing's been finalized but it's most likely a Malboro at this point. Everything seems to be going well for the heroines until Mr. Malboro does his burping thing for crowd control. Marlboro toxins leave them staggered closely around him for a few fateful seconds, at which point three of his tentacles lash out and quickly find their targets in unarmored belly buttons (minor clothing malfunction there, girls). The tentacles serve as a Corruption Juice delivery system. The Malboro itself sprouts some nasty mushroom-like formation that encloses the immediate vicinity so none of the goods are damaged during gestation. A few seconds / minutes / hours / brief timeskip later, the Not-Gullwings spawn out of the mushroom in a cloud of spores. And then... I don't know. I usually leave at least one or two other characters standing around for the corruptee(s) to brutally kill off and establish they have, indeed, crossed the line, but that doesn't really work with the whole group assimilation angle I have going here. The lack of an ending is like the main thing that's holding me back, aside from wondering if I should tone down the part with the surprise navel invasion.
The weird thing is I was looking at random FFX-2 videos after I came up with this idea and saw one of Yuna's dressphere changes involves her blossoming out of a giant flower, so this does actually have some kind of precedent in the context of the game.
I was planning on giving the girls a mutant Spriggan motif, though. Yuna would still have her short shorts but her skirt-thing would made out of lily vines. Rikku would have sunflowers growing out of her ponytail and a new leaf bra. Payne's warrior outfit could be redesigned so it looks like it's made out of black rose petals, etc. They would spend the rest of their time as nature spirits guarding their forest / Father Malboro / whatever. In another universe, this could have been a clever allegory for the Greenpeace fads of the 1980s instead of just some dumb exploitation fanfic.
Working title: Fun Times with the Fungi