Proceed as planned. At this point in the construction and the information provided you are most likely better off doing what was planned.

I rarely ever use a tub, so I would want a master shower to be wider than 36". If I could not fit a larger shower in my master I would give up the tub and make sure that a secondary bathroom had a tub.

The only suggestion I have is that you could swap the shower position with the toilet position. Then you could increase the width of the vanity (or maybe add a tall linen cabinet like in the photo you posted), and possibly increase the width of the shower by 6" if desired, if you slid the tub to the left about 6" or so. Otherwise, the design you have looks fine to me.

@Emily are you talking about something like this? This is another lay out we considered...we’d have option of door or no door on the toilet, but it seemed a little closed in?

@M t, Yes, except I envisioned the toilet rotated to the left, so the tank was on the same wall as the vanity, then a partial wall between the vanity and toilet, not a separate room, because your bathroom is a little small for that, unless you do the slant wall you picture above. In my plan, you might have to lose 6" off the shower length (to allow toilet access) but could add 6" in width. I think any way you do it is going to be fine, but I'd discuss with your builder and get his/her input and recommendation. Good luck!

@Emily Thanks so much! That makes sense.

@M t I hope you'll post with the final decision you make!