I did just what you describe and I'm tickled pink with it. In my case it WAS a load-bearing wall, but that just meant I had to header off the opening. I created about a four-foot archway between the two sections of the (now one)room - making one section the bed area and one the sitting/dressing area. I can't tell you what it costs since I did it myself, but I really don't think it would be that bad, depending on what needs to be done. I had to move a electrical box and add another (to stay up to code) but it was mostly a framing/drywall job. I would say the most important thing is visualizing the feel/scale of the new room as well as new traffic patterns and usage patterns to come up with a good design. In may case I created a couple of new walk-in closets to keep the scale of the resulting room comfortable. I know I've been in several "de-partition" rooms that feel just like that - two rooms with a wall knocked down.

When we build, there won't be any rooms above our Master Bedroom. At the moment, my almost 13-year-old son and 3-year-old's room is over our Master Bedroom. My 8- and 10-year old's room is above the living room. Their bathroom is between their two rooms. When sleeping in, I can hear every single movement that my 13-year-old and 3-year do. There was carpet in the room which helps with the noise, but I hate carpet and put in wood flooring. If he drops something, I hear it. When he goes to the bathroom, I hear it. When all 4 of them are in one room, I can hear them. Just as this, I can hear every movement in my other boys' room when in the living room. They are very rambunctious and like to jump around. Another problem I have is that the pipe from their toilet/tub goes down the wall which is located between our living and kitchen/dining room. When they flush the toilet or let out their bath water, the pipe rattles in that wall. I know every time they use the bathroom and so do my guests. Most times it is rather embarrassing.

So I just tweeked your current plan a little bit by doing pier style cabinets on either side of the bed. Then you don’t have to have a nightstand. Or you can just do full height wardrobes. You will have to account for the jogs in the wall so that the bed is positioned so that you can get the doors open. Then the desk would be opposite the bed and possibly add a little bookcase. I am showing a queen sized bed.

Guessing the window is there for curb appeal on the front façade. Have you drawn a mock up to see what that would look like? Sky light /solar tubes add TONS of natural light!! Gotta wonder who the architect was and if it would be cheaper to move the closet so the window is part of the room, than mess with outside walls!!