Are you writing the essays for them or helping them write their essays? Why not just partner with a service like Essay Edge that has has already dealt with these concerns?
Our software(not me) assists our clients it expressing themselves. It asks dynamic questions(based on client's country of origin, personality, education, work, passions, life goals) in order to help applicants organize their thoughts in their distinct voice and overcome the intense biases that they are facing(Most cultures just don't do personal essays, and modesty kills most applications). The output is unique but follows a basic outline. Students later add information or make edits as needed so that they can produce their own work. We sometimes proofread their post edits.