Tile is still the best thing for a walk-in shower to be waterproof. Neither the cork or hardwood will be. Think about installing a radiant floor under the tile like Sharon recommended. I like the NuHeat Radiant floor system the best.

When installing over top of old ceramic/porcelain be aware that you will most likely have to "sink" the old tiles in cement to do this. That means grinding down the tiles a little (rough up the surface) then the self leveling cement is poured and allowed to dry. The new floor is then laid over top. Vinyl is notorious for requiring EXTREMELY flat surface. A ceramic tile rarely has this requirement (grout lines and "high spots" around tile corners give problems). A glue in place tile is also going to have the same problems and the same solution = sinking the tiles in cement. This adds extra costs to the floor. A rigid floor like a cork floating floor can handle a bit more floor deflection than vinyl or laminate planks. If labour in your area is relatively cheap...you could probably have the tile removed and the sanding of the mortar done for the same price as coating in concrete. You will also have the luxury of being able to lay any floor you want once it is done AND you don't have to worry about increasing the floor height. It is possible to sink the ceramic in cement...but is it the most cost effective option? Maybe not.

You should remove the cork first as tiles need a flat and even surface to go on. Definitely remove the cork.

I was going to say. There's no way that carpet could be in here, especially when animals aren't always the best at making it to the bathroom in time. Great article!