If it would be of value, I'm willing to contribute my time to rewriting submissions (i.e. writing new, parallel texts with the same content but completely new phrasing). I could try to make a point of writing in a style unlike the original, or in the same style for all stories, etc.

English is not my native tongue. I would preserve the intent and content of the submissions, but I can't promise the quality of the writing itself won't suffer. OTOH, this might further obscure the true author

Of course, the rewritten versions would have to be approved or further edited by the original submitters, and I would not know myself who submitted each response.

Would this help?