Updates in response to feedback:

-Smaller sink.  this sink from Twyford sits back into the wall and has a much smaller footprint.  Face-washing is potentially an issue, these basins are mostly meant for hand-washing.

-Toiletry cabinet with mirror - keeps things organized and out of the way.

-Compacted space.  With the smaller sink, the footprint needed is far smaller and can be moved directly next to the toilet.  Sink helps to keep some water from raining down onto the toilet paper holder.

-Bench replaced with fold-down seat - no need for both the toilet and the seat to be in use at once for steam/shower use.

-Two solutions for the issue of tracking water in and out of the house: either a roll-up mat with holes for drying (similar to this like restaurants use) -or- bathroom sandals that don't leave the bathroom - they're kept just inside the door and taken off when you leave.

-And in response to those who like spending time in the bathroom - I do as well, the shower is the best place for thinking.  Having a window in the bathroom makes it feel a great deal less claustrophobic, and also helps cut down on mold and mildew.  

I understand the appeal of a long soak in the tub!  Baths do use a great deal of water, however, and in sauna mode a little space will steam up much faster than a big one.  

Another fold-down bench could be added to the opposite or adjacent wall, or the one could be longer...depending on what kind of company you have over :D

All down to the end user's preference, of course - but in a space like this, cutting space out of the bathroom may mean a bigger couch or more storage space.  Depends on your priorities!

Original idea text below:_________________________________

Some have bathtubs for soaking, some do not.  The shower is a generally a handheld affair that hangs on the wall, and there's a small sink and mirror. There's generally little to no separation between any of the functions, and in most cases the walls are plastic or tile and the entire room functions as the shower.

Aside from actually sitting in the bath,  we don't spend a ton of time in the bathroom - why devote so much space to it?  No reason not to have the entire set of bathroom functions take place inside the shower. 

Most things in the bathroom can get wet without harm (toothpaste, toothbrush, soap, etc) - the only thing that can't is the toilet paper, which could be stored next to the toilet with a snap-in, waterproof cover.  Towels and clothes are hung outside the bathroom door on a hook while the shower is in use, and the bath mat is just outside the door.  

Plus, cleaning is a snap - scrub down the walls, sink, and toilet and use the free-arm shower to rinse.  

And with a little clever insulation and a steam pipe, this is easily convertible to a sauna.
I'm on the organizing team, so I'm not eligible - please steal this idea for your own designs.