The adjacent half bath will be very small.

we will have a in wall tankless toilet

I will try and find my half bath inspiration photo.

While it may seem desirable to put in something smaller, form should follow function, so ask yourself some important questions: Who will be using the space and what are their needs? (space to set down hair dryers & electric toothbrushes, curling wands, etc) How many people will be sharing the vanity? (Will there be two people trying to use it at the same time)? What are your storage needs? (What space do you need for make-up/appliances/toiletries/cleaning supplies, not to mention towels)? Will there be a separate linen closet nearby? Once you answer these important questions, you'll likely have your answer. Good luck in your renovation!

Here is my inspiration photo for the half bath.https://www.houzz.com/photos/modern-powder-room-modern-powder-room-san-francisco-phvw-vp~99121800

We plan to make the full bath into an ensuite with an existing bedroom. The new half bath would service the main floor where the living room, kitchen and sitting room are located. It is located off the entry. We are also stealing a little space from the closet to make the shower bigger. The house is currently a rental that will become our retirement home. In the full bath we plan to put in grab bars and a curb less shower. I don't think the full bath is of a size where two people will be using it. As far as storage goes there will not be a linen closet so the vanity will have to take care of all our storage needs.

I would continue with a banjo counter top with the mirror extended the full width to make the room appear as large as possible.

That is a good idea Beverly. Although we have an existing banjo I had not thought it would work in a more contemporary space but seeing your photos makes me re-think this. I also like the functionality of the large mirror and you are right it will make the room look bigger. Does the scale of the current banjo look correct?

You need 4x4 for a curbless shower, and there is zero point in doing the expensive structural work for curbless unless you make the rest of the bath accessible, including a wider entry door.

Your concern with the banjo would be that there is enough room to get at the internal plumbing in the toilet. Double check the height of it.

There is currently enough room to access the internal plumbing of the toilet but I am glad you brought this up as we are thinking about having a taller toilet installed as I was told it is better for the elderly or someone with mobility issues. If we do that can we still have the banjo? If not we are going to put a grab bar by the toilet so hopefully that would be sufficient.

Sophie, our bathroom designer reccommended a curbless shower base that he uses often and he said it would work in our space. Yes, we plan on having a wide entry door. I do agree it would be preferable for this bath to be bigger. The shower will also have a bench that will fold back when not in use and shower controls you can use while seated along with a grab bar.

My husband's parents are getting older but fortunately at present no one needs these modifications but it just seems wise for these to be in place.

What do you think of my tile choices for the half bath?

When curbless goes wrong because it’s too small and waterproofed incorrectly.

I see the problem. You are quite right Sophie. My plan is of the existing bathroom but we are making it bigger. I should have emphasized that more in my intro comment. The new shower will get additional depth from the coat closet and be slightly wider - I can't remember if it is four or six inches.

Having taken months to recover from a broken leg, a small curb from a shower was hardly an impediment. In fact, the tub was hardly an impediment so long as I had a bench that was accessible from the outside of the tub that I could slide onto. Not being able to stand safely for any length of time is more an issue as we age.