Your inspiration pics did not post.

I’d remove the existing shower, tile the entire bathroom floor and put a tall storage cabinet in that area. If you have another tub in the house, you could replace this tub with a nice big step-in shower with lightly-frosted sliding-glass doors, tiling the shower floor and three walls to the top of the shower space. The shower could include a tiled built-in bench. Clear glass needs to be squeegeed every time the shower is used, but if your tile is pretty, I would use clear glass to help the room feel bigger and show the tile.

Dimensions please.

Yikes!! Sorry, here are inspo pics. Not necessarily loving all of the “styles “. But the ideas are similar

IMO it's a bit tight for a makeup area . The shower screams closet.

Linen with drawers

For your vanity area, a linen closet like this might work.

Another version where the storage is on top of the vanity.

If you don’t use or need a makeup vanity, then just make the shower into a closet or a built-in cabinet type linen closet with drawers like posted above. And you can simply put the swinging door back on because it won’t be annoying because whatever closet will be less deep than the shower.

It will be an incredibly deep linen closet! Do you want to grab some of the space for whatever rooms back onto the shower? You won’t need the linen tower in rhe bathroom so use that space for your makeup area. Be aure that the door swing isn’t impeded by your stool or chair.

Use the shower area for storage and leave the sink countertop free and clear. Under mount sinks are best in a bathroom because they don’t hog the countertop space like vessel sinks do.