Does the shutoff valve have to be in the shower? Could it be moved to the other side of a wall outside of the shower? The seems like the best long term solution, especially since you have to deconstruct the concrete block it's embedded in anyway.
From what I know of all of the "wet area" products you mentioned, you can cut the materials quite easily and put pieces together to build whatever you want. Once you have the walls and other structures put together, you have to tape and seal all of the joints to prevent water leaks. All of these products have tape/sealant specific to the product line.