In case we decide to use stock vanities, would two 48” work?
It leaves 3” on either side and only 3” between the two.

I vote no. The "seam" between the two would be dead-ahead of the door ... it would be your sight line as you enter. It would annoy me to no end.

I'd also flip-flop the toilet and the shower so you can have a window near the toilet, where it would be useful ... and a window in a shower is always a bad idea -- water will win.

Last thought: I'd go with a hinged door (perhaps near the bedroom instead of the bathroom?) because pocket doors are bad news in a bathroom -- they're great for doors that are rarely closed (like a laundry room or a pantry), but bathroom doors are used too frequently for them to be practical. OR, because this is a bit tight, this might be a case for two small double doors (like two 18" doors) ... if you put them on the right kind of hinges, the doors could "fold back" against the interior bathroom walls.

Though that brings up another problem: Where are your towel bars?

If you do freestanding separate vanities, no bigger than 36” each. Hamper between.

I love pocket doors in the bath. We have one in our master bath and it works great. Used every day for 15 years without a hitch. I also put in a vote for a window by the shower. We are embarking on a remodel and will do a switch between toilet and shower to move the shower by the window.

I think the 2 vanity idea is not so good but really like your proposed layout. edit - just saw Sophie Wheeler idea and the hamper setup sounds good as well.

Rhumbob and Sophie Wheeler,

At one point we had the toilet and shower reversed, but realized how much nicer to have a transom for daylight while taking a shower. I really do not want or need a "view" from the toilet. Daylight would be nice but only one location can have it.

I spend more time in the shower. LOL!

I think I am returning to custom cabinets being built. 36" vanities is probably the maximum as Sophie states, and that is too small for my bathroom vanity space in this new home. :)

Think about your sight line as you approach your bathroom...what do you want to see? I wouldn't want to see a hamper with dirty clothes stuck in the middle of two vanities - that paints an awful picture in my mind. Try pricing out custom...it may not be as bad as you fear price wise. I would try to do two 42's - and a 18-21 inch stack of drawers between the two. And a beautiful countertop spanning it all. This gives you a lot of center vanity space to put something beautiful front and center on the countertop that you will see with that sight line from afar. I believe you indicated that you have approx 105" total to work with (two 48's with 3" on each side and 3" in center = 105).

The original poster's comment was that she was considering two 48's leaving 3" on each side and 3" in between...thus implying she had a total of 105" to work with. I was trying to reconfigure that space a different way with the 42 21, 42 so that visually as you enter, you see nothing but pretty cabinetry.

The 18 inch center cabinet is probably more accurate. You will likely need some space on the ends to clear trim, especially if doing a frameless cabinet. The drawers will need clearance for any variation in the wall as well as door trim around the toilet area door, possibly baseboards if they are tall.