I'm building/constructing mini shower/toilet in the basement. It's really mini (ship like size)180x80 cm (~6x3 feet). So it's important to waterproof as much as I can all the room. The base is concrete slab (all walls are interior), then should go membrane, the sloped concrete bed, then I thought red guard on floor and cement backerboards, then modified thinset and glass tiles (2x2") on the floor (and some inserts in the walls between glazed ceramic tiles). I think to use epoxy grout for the floor, but not sure if I can manage on the walls. The question- is the work process and material list is OK and how important to gout shower walls with epoxy too. That is all about red guard and glass tiles being not penetrable to the water, but regular grout on walls can create a problem?
Any help would be appreciated.

I've read a lot discussions about the glass tile on the floor, but slippage doesn't bother me, the space is too small and the shower will be used very rarely (more for emergency and guests).