We liked the 1/16" look for ours. Our colors are practically the reverse of yours--grey tile & pearl grout. We have a combination of 3x6s (top 2/3 of the shower) and 10x13s (bottom 1/3) separated by 1x12 decorative glass listellos. To me, the grout lines always look a little larger when complete anyway, so I would go smaller rather than larger. Plus it's less space for anything yucky to grow! Just my $0.02

We have an historic house and I can relate to your considerations. It's one thing to use a ubiquitous material, but not sure if you want it all over your house? And I can understand for resale value you wouldn't want it to look like you got a volume discount on the same exact type of tile. What we ended up doing was premium 3x6 white subway tiles in the tub and chair height walls in the main floor bath. In the secondary (finished basement) we did basic 6x6 white tiles in the shower, and beadboard wainscot on those walls. I feel the bathrooms compliment each other well and fit the period of our house without being exactly the same. We haven't done the kitchen (I've been scared off of renovating ever again ;) but if we do, I am considering either doing a sheet soapstone backsplash, or some green fireclay-type tiles. I would suggest you browse some local real estate listings and see if you can find any houses that match your level of renovation and sensitivity to historical materials. See what materials they've used coordinating throughout the houses. A lot of it is going to be region-specific. I love to attend open houses of 'time capsule' homes and see what they used. Around here in the 1920's era homes, there's generally a white bath on the main floor and a colored tile bath elsewhere. Kitchens have white subway tiles, but they have a bit of a different look, definitely more utilitarian. GL!

A rolling shower, probably means what we call a "roll curb", or "curbless". Now, for the MOST part, your selections are just fine. This is complicated a bit as the extent of the height for the "roll" generally needs to be high enough to allow for door passage if say there is a rug outside the shower and the door needs to clear it. The installer's concerns about the tile on the floor , a 3" hex, could be legitimate if the a 3" tile can't comfortably conform to the required height of the "roll". Other than that, a good tile professional can install that tile to your specifications. And yes, he would work with the GC to make sure that the substrate is proper. If it was ripped to the studs, that should certainly be accomplished. That tile is not what we would consider a "challenge" (other than what we noted about the size of the floor tiles and the potential height of the transition from bath to shower floor). Would add that when working with natural stone, make sure that the installer (a new one) lays it out in advance so that you can agree to the shading and pattern. There are "whiners" in every occupation or craft. "This is the problem, that is the problem". In our industry we all know who they are and avoid them. They are often not capable or they do not take pride in their work such that they have low expectations of themselves. Ask your GC to bring in the "A team" (and do consider the floor tile selection/height of the transition). Have these discussions with the new installer as onsite consults and discussion with qualified professionals will trump online discussions all day long. Good luck with your project.

They need to be rated for floors. Should say on the manufactures paperwork.