The usual worry is how to make a shower totally waterproof, so as to protect the rest of the house from the effects of water. A closet opening into a shower space is going against this goal. It seems far better, to me, to make the shower a bit smaller and put the closet next to the shower,

So, do you live in a climate that is mild year-round? If you are able to have uninsulated attic space right across a wall from your shower and have no freezing, no condensation issues, and no need to care about the temperature of that unconditioned, non-insulated space, you must live in paradise! Are you certain that you don't need to insulate? You don't want towels in that closet to get damp because they happen to live where warm, damp air meets cold air.

I live in dry SoCal, and I'd be worried about linens getting damp from such an arrangement. Also, what if someone needs a towel and someone else in in the shower?

Maybe someone who has an open shower (I want one!) can say for sure, but I think you don't need 8'. My sister has a shower like this and I think it's more like 5'. In any case, I'd make the shower shorter and place the linen closet outside the foot end of the shower.

I don't really think you would miss much by having the shower be 4'4" x 5' and having 3' left over for a linen closet. Not enough to go to the extent of a waterproof hatch.

Just to put things in context: Three old-school "standard" baths are just 6" shy of fitting into the space you have. You should be able to get a decent layout with a large shower in there somehow:

I would appreciate any thoughts on the bathroom reconstruction plans. Everything is being gutted, so anything could go anywhere. The only thing we may keep is the vanity, but with a new top. We want a big shower, prefer it to be as open and doorless as possible, and want it along the unfinished attic wall area to avoid the large window on the opposite wall. Yes, that wall is well insulated.

Me again, glad to hear your attic is insulated. I have no idea why I fixated on that last time, I think I was just imagining cool towels meeting wet air and seeing condensation happening all over them!

Anyway, what a nice space you have to work with! With a bathroom, though, fixtures tend to hug the perimeter of the space, just as you have drawn the room. It makes for a nice 6x8 space for dancing in the center of the room, useless for anything else, since the two of you will be crossing it in so many different directions! So twirl your partner when you happen to meet in the center.

You could possibly change the direction of the tub under the window so that the foot or head of the tub were directly under the window, and the tub was jutting out into the room, kind of parallel to the toilet wall (or is it a half wall?). For this to work, the vanity of the tub user would be moved over to the right, so that this person kind of walks around the tub a bit to get to it. You could put in an "L" cabinet there, giving the tub user a bit of a sitting vanity at the South end of the window (lets pretend this map is done on the NSEW coordinates). Day lighting and makeup table may go together well. Or not.

Back at the current vanity area, we have possibly created room to insert a shallow Towel Tower 2' - 3' wide and as high as you like or need, between the two sink vanities. Try to keep it 1 ft deep, as the other occupant still has to squeeze past on the way to the vanity on the right. Maybe the towels can be rolled and placed into a grid, so they will stack while rolled and slid into their cabinet. Like bottles in a wine rack.

The other obvious place I saw for a towel-holding piece of furniture was next to the door as you enter from the closet area. If the little potty alcove is as small as you have drawn, a dresser could be placed there to hold bath linens. I will go shopping at Pottery Barn for an example, and post it here.

One way to make your walk-in shower not need any glass door or shower curtain would be to curl in the "wall" or "glass" that is represented by your dotted line. By simply adding a curve to that wall and making the entrance walk a little bit past that curl, you will keep most of the water of the shower contained. If you want to be sure that steam escapes so the shower will dry out, you have a good fan exhaust system to run after the shower, and you do not have the shower walls go much higher than the head level of the occupants. If the walls are solid, people may appreciate having such a large shower be low enough to see out of, as well.

Here is a link that might be useful: dressers to hold towels

Your doors in your plan look like they will be a problem with bumping into each other. Have you considered pocket doors or opening them into the room instead.

I know this an old post but I wanted to show the solution we came up with. i dont have the most updated pics as we are waiting for the glass for the shower

We had an 8 foot shower, it is shortened and now allows space for a linen closet. the closet floor is sloped so water wont run in. there is now a frosted glass door on the closet and glass shelves are being custom made for the closet. there is a motion activated light in the ceiling of the closet