Adding a quality washer dryer in the kitchen is similar to adding a dishwasher. There is no need to waterproof, however, it is to be noted that you won’t have a laundry trough. If you keep the sink clean and free of grease, it would be easy enough to use the sink as a laundry trough.
I have designed many kitchens with a washer dryer in. The quality units (usually European) are almost silent, and they do not emit much heat in the dryer mode.