Most my doors were already here, but I did have one moved over, about 6 inches. However, the entire space was demo'd, and rebuilt, so that's not the best example to draw from. If you want the door hidden, in a pocket, yes, you will need a skilled carpenter. Essentially, the opening header and frame, will become twice it's size, with the "pocket" part, hidden behind the wall. The studs/supports will need to be removed to make a space for the door to slide into. Do you have any switches or outlets on the fireplace wall?

How do you decorate your place, what kind of style, colors, and feelings? That will greatly influence the type of door you might want. Also, think of your budget, and whether you want to install it yourself or hire a professional (you don't need to tell us, just keep that in mind). Then look around Houzz, in the products page, they have lots of interior sliding doors and hinged ones, from elegant frosted glass in a dark wood frame, to rustic reclaimed wood planks. You may not want to purchase that exact model, but it might give you a better idea of what would fulfill your airflow needs without sacrificing style.

If the door is well painted I doubt if you will have a problem. A good coat of paint on wood work and wall surfaces is important if you have a lot of moisture in the room. If you can do some alterations to the space I would suggest you install an exhaust fan in the ceiling that vents moisture to the exterior, i.e. through the roof or side wall. Companies like Nu-tone and Broan make fans that have a moisture sensor that will kick on the fan while using the shower if you forget to turn it on. And these fans can be much more quiet than the typical bathroom fan. Some hundreds of dollars for the purchase and installation of this would be well worth it. I have seen bathroom ceilings covered with mold because the room has neither a neither a fan or window so you are right to be concerned.

Hey Farooq, I understand your concern. I have a better idea. Drawing room and Living room does not need to be separated by a wall , you can just have a step up wooden flooring done in the drawing area to define the space. Also as per the plan what I have sent you, you can create a window where you existing Main door is and open up the Main door from drawing room as shown in red. If you still want want a wall between drawing room and living room then you can have it but it's just that I feel you can make your living room look big if you knock of the wall, or you can even create a partition with Jali work or you can even have a low height wall to just define the area. check out some of the images attached :)