Drop the shower floor in the slab or framing to allow for a curbless design with a linear drain. You can use one giant tile (neolith for example) or large format tiles. 48x48 is not uncommon.

We did exactly the same thing on our shower retile as Cabot & Rowe suggested above, although we used a smaller tile (12" X12") with 1/16" grout lines and epoxy grout, and it's not an issue as far as keeping it clean. If you use large format tile, just make sure that you choose a skid resistant tile with a COF (Coefficient of friction) of 0.60 or greater.

For another, smaller shower we had tiled, we knew the large format tiles -- 18" X 18" -- we were putting on the walls would be a little too slippery on the floor, so there we put in a 2" X 2" mosaic to have more traction from the additional grout lines.

I've done large format tile and I've done single-slab natural stone pans. Last single-slab was a pan formed out of slab of soap stone. Soap stone is pretty easy to fabricate so I did that myself.

You can also use man-made sheet materials, but that might not be the look you're going after.

Small comment...not sure of how the house will be lived in or who will be living in it or what hours the occupants will keep...but one thing that immediately caught my eye is that your master bedroom shares a common wall with the great room. If noise transmission might be an issue from the kitchen/great room, you could move your closet over to be a noise buffer on that common wall.

MongoCT, like I said, we're not terribly picky about the material for the shower if we can keep the grout lines as minimal as possible. For the master, we're actually having that entirely insulated on the interior walls. I think that should be sufficient maybe?

If you are worried about grout maintenance, consider the newer single component grouts such as Fusion Pro, Flexcolor CQ, or Plasma

Just curious if you're planning on running laps in the shower?

Sjhockeyfan325, you know, on those colder days, it makes it a lot easier to get a few miles in.

Ha ha - good point!

That's why those non-slip tiles are important....

Too funny. I hope you both are very warm blooded because a completely open shower that is that large WILL be chilly. No doubt about it. We were in S Africa in one of the camps and in an open shower a bit smaller than you're building. I was so cold, I couldn't wait to get out of the shower.