Re: What's an improvement?
You may consider opening a wall up to complete your design. It is in style to have a very large shower but to do without a bathtub is another question. If you have a 2nd bath with a tub you may want to consider the closet option and eliminate either the bath or the tub. It is hard to tell about the values but, I suggest that if you only have the one bath keep both.
At one time we added a seperate shower in the laundry room this was very convienient. You may want to consult an Interior designer or Architect it would be a good investment to do this.