It makes sense to add the walk-in closet at the end of the space opposite the window. You have a lot more length than width. This will help square up the room a bit. Get rid of the existing walls, and build out as far as you wish, perhaps to within a couple of feet of the window.

Have a walk-in closet for the entire length of that wall. There is no reason not to

Yes full length for sure.

Since the room is long, you could do something like this idea..Instead of a built-in headboard, you could have a regular bed. Look at the project and you will see other angles of the room

Sims Hilditch, Radlett Family Home · More Info