You're thinking about it too complexly. Just change the textures to be that all of the face textures are the stitchface turnip. They're located in the common3 in the system folder, in the following ARCs/BRRESes, etc. in BrawlBox:
ItmCommonBrres -> ItmPeachDaikonBrres -> TextureData[0] -> Textures(NW4R)
Just export the stitchface texture, and then "Replace" all the others with the same texture, and save.
Just tried this, I can confirm this works, but only changes the texture of the turnips. The turnips hitting properties aren't.
I need Peach to pull out her stitchface turnip with the hitting properties of it aswell.