From just seeing the plan, this looks like a large bathroom with a decently functional plan. The beauty of a wall and door around the toilet is that one person can be in the toilet while another person is at the sink. Also, the - ahem - smells are more contained so a person can go to the toilet, turn on the fan, and close the door, and the smell won't disturb them while they shower or bathe. If that isn't how you live, by all means, tear down the walls, but you don't have to move the toilet to remove the walls.

You talked about moving the tub and/or expanding the shower, but I'm not 100% clear about what you don't like in the current layout on that side of the room. If you're just looking for a bigger shower, I'd take out the linen closet. Expand the shower that way. Then, put a tall cabinet between the vanity and the bathtub (no pipes need to move for this plan, let me know if you need me to do a quick sketch to show what I mean). Or, turn the toilet and put in a new linen closet to the left of the door (the toilet would only need to move a small amount, quick sketch below)

I estimated the dimensions I didn't know from your plan, but here is another version that involves more changes to the plumbing overall, but no change to the toilet and you get a double shower while keeping your bathtub, linen closet, and double vanity. Again, rough sketch. This plan would involve doing something to work around or move the window.

I’m also a fan of the enclosed toilet. Your general layout looks good. I would go for a longer vanity for more counter space. If you’re keeping the tub I’d enlarge the shower by raking the space from the linen closet, then would add a linen cabinet to the bathroom side of the wall that encloses the toilet.

I’m no artist! If you do take out the toilet enclosure I would think about putting at least a pony wall there for a little privacy. I wouldn’t buy a house without a separate WC, personally.

Last suggestion I'll share. No problem with the window in this one, no moving the toilet, linen closet, or bathtub, just shift the double vanity and get your double shower. This one is my personal fav but does still require some plumbing moves.

To move or not to move........Use pony and glass. There's no advantage to the totally exposed loo. The inches you have, are the inches you have, and the tub, and the window are the obstacles to a decent shower,adequate vanity space. . Double shower heads, simply close in the shower. Give something up.......or use the bottom with two heads below. Either way? Lose the tub.

Thank you all for the recommendations! I sketched some layouts before reading your comments. And was considering going for this layout with the tub (see pic). Now I kind of rethinking if we should lose the tub since there’s a tub in guest bathroom already on 2nd floor and another shower on main floor. If we go without the tub, we were thinking to make a 36”x99” double shower (issue with that is finding the glass door that would work), or make the shower 36”x72” and build some shelves or storage space for remaining space (27”). Is 3’ wide shower too narrow nowadays? As for the toilet, maybe we can just remove the door? Feel kind of gross having to open the toilet door right after using the toilet since vanity is outside of toilet room lol. Also feel that enclosed walls around the toilet make the room seems much smaller, no?

Here are the sketches

Do you actually close the door when using the toilet? Ours rarely gets closed, the room just provides visual privacy from others in the BR.