I am trying to determine best way to add space to second floor of my bungalow?

I have a 1920's bungalow that right now has 2 bedrooms upstairs. The chimney rooms smack down the middle of the house. There is a another roof line that pitches the opposite of main roof creating eaves or attic space in the front of house. This space has been finished to create walk in closets and bath. The back of the house has a lot of wasted space with the pitch of the roof line. If I raise the roof and bring it straight out, what's the best floor plan for accomodating the chimney in the middle. Ideally, I'd like to add another bath and bedroom.