Can you post a floor plan with ALL dimensions? It would help you get good advice.

80K and a good K&B designer is where to start.

That’s what I’m afraid of!

So many possibilities it just depends on money and how elaborate you want this to be. If you don’t need this room to be as large, do you want to make it smaller and use some of the space for another purpose?

If you keep the room size the same, you could:

In the space where the tub is now, have two vanities back to back with a floating double sided mirror in between.

You could be simple and lazy and throw a circular settee in the middle of the room to take up space and call it a day.

Kendrah has some good starting points. The first decision is whether or not to keep the room the same size. If you do, there would be more than enough room for a makeup table if you don't already have one there. As others have said, it would be helpful to have a dimensioned floor plan in order to get more useful comments.

You posted this same dilemma in 2019.

Increase the size of the shower and put a vanity on the right side. Add a linen closet and space for towel bars/hooks.

Yes,,,,,,,,,,,,it's been six years, same bath, same problems.

https://www.houzz.com/discussions/5821301/master-bath-floor-problems

How long are you staying in this house? Why? Because you either bite a bullet and get going, or when you do move, be willing to suffer the pricing that will reflect the UGGGHHHH of carpet in a bath- nobody but nobody wants it. That is just a truth. Add to that, you remodel for you, not another stranger, so timing should allow you to enjoy it!

Until you post the floor plan that shows the entire oversized primary suite, sitting area, detailed every dimension, ESPECIALLY the bath ( every solid wall, window, and every dimension for everything, , it will be hard to get really relevant help here.,

In order to "re work the cavernous space", it all begins with feet and inches . Add jpegs of ALL the bath, not just the window view. Where is the potty, where are the closets, The entire primary suite as a designer would see it, were you to invite one into your home.

Otherwise.....all you will get will be loose suggestions, a hundred or more ideas, and be back at 2019: )

I could not even beging to guess with one picture . You need to post a to scale floor plan of the bedroom, closet and that bathroom all done to scale on graph paper showing every window , doorway where those lead and every meausrement clearly marked posted here in a comment in jpeg format. I hate huge bathrooms they are useless and honestly I clean mine every day so no way 400Sq ft for sure . I can understand 6 yrs to wait to do this huge job so let us help now by posting the plan. This will not be cheap but IMO worth every dime to do