I'm not sure how your warranty laws work, but in the US the warranty cannot be voided in whole. For example, changing out your lights and perhaps a bumper cover could not affect the failure of an otherwise-covered powertrain component, etc.
That being said, unless the parts are virtually free, I'd avoid doing this as well. To each their own, but if the 2018 look was that important to me, I'd simply go get one. But everyone has a different situation and a different outlook...different strokes for different folks. If you do it, post up the before, during, after, DIY type stuff for the next person!