This concept is a bit out of the box. I have a master bath with a large 80's Jacuzzi tub that is going to be remodeled. I plan to replace with a new tub/shower. The alcove it is in has high ceilings, is 7' wide and is at the end of a somewhat large space. It is seen from (no doors) the master bedroom and so I am wanting to create a somewhat dramatic design without having to use tile. I believe that I can achieve a watertight, leak-proof installation if I ask my contractor to install cement backer board with Schluter membrane tape at the seams and joints and/or painted with red guard, as if I was going to install tile. But then, instead of tiling, I want to stencil the walls using a high adhesion primer and exterior latex paint. If red guard is carefully applied, will the finish be somewhat smooth or is this a bad idea? Thank you all for your thoughts and pro advice!