I'm going old school and just dry packing it but with a seamless pan liner and infinity drain. Maybe use one of those Quick Pitch jobby's. Last guy had none of this new stuff and the first step down pooled water against the wall. It was dry pack on the concrete slab.
Notice the installation method the installer did, he buried the wall tile under the pan. It easily wicked up the wall and into the studs. I do my pan tile first so that the drip line runs down on the pan tile. Otherwise you can get cracks along the wall/pan and if upstairs is a reciepe for disaster.
I am water proofing the whole dang thing with http://www.mapei.com/US-EN/Tile-&-S...aterproofing-Membranes/Mapelastic-AquaDefense