Taking into consideration all your requests this is my project for your master bathroom.
In the floor plan I have showed all the dimensions of the walls changed or the furniture placed in. I haven't made any changes to the dimensions of the area you have given. As you requested, I placed the toilet where the shower used to be and also there is the storage area in front of it(where toilet used to be).
I placed new cabinets, in stead of the old ones you had. I didn't see your updated conversation with the other client that's why I changed the mirrors.
Bringing more light to the bathroom I placed ceramic white tiles for the walls and beige tiles for the shower area. According to your request I tried to keep the shower area only a few centimeters higher than the floor level(2"-3"). I used hardwood for the shower area, so that it feels more comfortable and it's not so slipping.
Furthermore I added a sitting bench as you requested in the dry area, the one in white wood. It is about
1' 7" from the shower level. I also placed a glass cabin around the shower so that the shower area is separated from the rest of the bathroom.
I suggested hardwood flooring, so that the whole bathroom feels warmer.
In this second version I changed the cabinets and adding new ones made of white wood. I kept the 2 Robern mirrored medicine cabinets as you asked and also added a new mirror cabinet(center one/center pier tower) so that is combined with the 2 existed ones. In this version the wall tiles are placed till the bottom of the existing mirrors then the walls are painted in gray as you asked. Furthermore I changed the hardwood flooring, and instead of that I placed ceramic tiles
In this third version I made a change of the center pier tower. I also attached an image with dimensions of the cabinets and the center pier tower
I hope my work meets with your requirements