What about this bothers you?

Looks like flipping the shower and the vanities would open it up...... ??

There are a lot of windows in the bathroom. To come up with the best solution, there is A LOT more information that is needed. Contact a local architect(s) and talk to them about your wants and needs. Select the one you feel the most comfortable working with. A good architect is the best investment you can make in a home.

this master seems like a "wing" of a house. there are a lot of chopped up spaces, hallways, and rooms.. your right it doesn't seem right. ALL this space and a cramped bathroom? I would start wondering if you need a "sitting area" Also I constantly hear from customers that they added a tub because it looks pretty..keep in mind you are basically the only ones to ever see the master bath. Do you feel you will use the tub enough to cost the space?

The only change I would make is to get rid of the L-shaped vanity counter.
Straight counter with either two sinks or one long trough sink. 8' is plenty of length for a two-sink vanity.
I like the tub and shower. Regards, S*

I certainly agree with moving the toilet room door. I usually would not want a barn door going into a bath, however you do need to walk through the sitting room in order to get into the bath so that gives you better privacy. I don't mind having a longer area as you had drawn out for the vanities. They also could be split into two areas if you want more division. I would want to set up some of that huge space for an armoire for storing towels, bath supplies, etc. directly in the room of the bath itself. Just using below vanity space will not be enough.

You could use a beautiful antique piece of furniture for the storage. You could even have an upholstered bench in the center of the room for drying feet. Make sure you will have a properly sized exhaust fan installed which will go outside directly & not into the attic. I would be tempted to place the barn door on the sitting room going into the bedroom proper instead of the way you have it set up.

It looks as though you will have a balcony or deck to go out on from your sitting room. How lovely.

Based upon what I know about this project, which isn't much, consider this concept: