Instead of making a chopped up shower why not just install a shower on a wooden base then just indirectly drain it to the floor drain? Make that area a linen closet to keep access to the floor drain in case you need to open it up at a later date.
Or just use one of these http://www.mustee.com/product-lines/shower-stalls/
Or just use one of these http://www.mustee.com/product-lines/shower-stalls/