There are medicine cabinets with makeup mirrors inside although not sure about 10x.

Holes in walls are easy to patch. Your designer needs to pipe down. It is your house right now. Who knows what will happen in 5 yrs? You might move, you might not! Make sure to save some paint in an air tight container so you can touch up that area or just leave the mirror behind when you sell and get yourself a new one.

You might want to check around for some conversations on that black tile. I've seen some conversations of complaining the matte black shows a lot and can be difficult to keep clean looking.

I do not care for black or dark charcoal tile but that is my preference (i like the look at a restaurant but would not want it at my house). You could just do similar tile that is there but in a different color to your liking or what you feel someone else will like. I tend to shy away from the trends as I try to match the era of the house. My last house was traditional so i picked many traditional design elements. Current house is more mid century modern, so I leaned that way when we were remodeling.

In a bathroom, I absolutely would not use a dark tile, especially if it is matte. Every drop of anything, every bit of powder, hair product, hair, skin flake, will show up.