IMO remove the window or forget the shower being larger . Is the whole exterior brick ?Can we see the whole bathroom ? I cannot think of how to handle this unless you do a galss block wall to replace the window and there will still be movement visible but not anything obviuos . I have pixelated glass doors on all my bedrooms and bathrooms and you see movemment bit no way to see anyhing else

As long as this window isn't on the front of your house it might be OK to shrink the size of the window and fill in the part removed with siding (close to the color of the brick so it doesn't stand out). Leave a 18-24" high window, using the existing header (same width as existing). If the new window is quality vinyl it will be fine inside a shower. I had a small window inside my master bath shower in my previous house. As long as you have adequate ventilation so it dries out in between showers and clean it regularly it shouldn't attract mold. Think about how it will look from the outside before doing this, but my guess is that any future buyer will be happier about a larger shower and not as concerned about the exterior appearance as long as it isn't street side.

What is the floor plan of your bathroom? I ask because your current shower is quite tiny and could serve as a place for your toilet. Or it could become a nice deep storage area for towels, etc. I would then place your shower in the footprint of your tub and reduce your window’s size by replacing it with a glass transom of the same width. That would be the width of the new shower. In other words, fill in the bottom part of the window and leave only the top 12” or so as a high window inside your new large shower.

I added some more pics. Patricia, the whole house is brick. Glass block will not give enough privacy, plus, from what I have read it can get very hot, and the summer where i oive are extremely hot. I have a solar screen on the outside of tge window, and privacy glass inside. You can see too much for my liking in the evening after it gets dark. Kandrewspa I took a pic of my neighbors window outside. She shrunk her window and has white siding on it. Very unattractive on the outside, but beautiful bathroom inside. The window guy I had here said he would not touch something like that, it would ruin his reputation.

You're right, the neighbor's house is not a good look, but you could do a better job. Imagine if the white was the same color as the siding. It would be much less noticeable.

If you made the new shower as deep as the tub would it be large enough? Maybe you could go even deeper than that, but you don't want to make the space between the shower and vanity too tight. If you put glass on the shower wall next to the tub you wouldn't have as much of a closed in feeling. It could be a partial wall. If you really don't want the tub you could still remove it and put storage under the window.

What have a very similar set up. Here are two options I have in my head that we will do.

Option 1. Tub gets pulled out, wall goes also between tub and shower. Shower is now accessed from where the wall was (side) and not the end. Shower is extended down the wall and out as far as the edge of the window. I would put a wall at the end and have water on that wall but we are over a basement where access is easy. This would also give towel bar space.

Option 2 Tub goes, shower just gets extended down the wall towards the door making it longer, Our shower is 4 ft wide so it would probably end up 4 x 4. Hard to tell how wide your dimension is.

Both of these options leave the window as is. I plan on getting a top down, bottom up shade.

Take a look at some brick supply companies, see if you can find something similar to what you have on your home. Shorten the window as your neighbor did, but fill in with brick instead of siding. We did this a few years ago, shortened a window and filled in the gap with new brick. Our house is 30+ years old, and the new brick was a slightly different color. At first the new brick was somewhat noticeable - if you were looking for it. Now the difference is barely there, both the new brick and new grout have weathered.