Do you have actual dimensions for your floor plan? What you are proposing isn't the best plan, either for the dollars spent or the function gained. It will be especially difficult if you are in a cold climate. You wouldn't want to do the bumpout without a corresponding bumpout of the first floor, and cantilevering a bumpout like that will be significantly more costly than just doing a conventional foundation and two story addition.

If we knew the dimensions of the existing bedrooms, halls, and baths, perhaps a few things could be rearranged. And, if we also knew the source of the conflict here about using the existing bathrooms, that would help as well.

Have you considered closing in the open foyer? Then using bedroom 3 for a bath and closet? That would give you better temperature control and sound control in the house, and be a much easier project than a bumpout would be.