I need to see the actul house and the drawings of the new exterior. I really dislkke toilet rooms inside bathrooms to be honest if anyone ever used the toilet while I was in the bathroom they would forver be locked out until I was finished . I really see not real advantage to making the bathroom that much larger for no real improvement in layout so I would make that space a bit smaller and a lot more user friendly . As for the office I guess if it needs to be larger than that is taht . I think a lot of money and work for little pay off.

I don't have many drawings of the exterior, but hopefully these help. We are adding a garage which is on the first floor part of the drawings. The bathroom is the top right window. There is no dormer on the existing bathroom, so I gain a shower I can stand in, an additional sink and my husband's insistence on a toilet closet. There is a full bath downstairs, but this will be the main bath upstairs.

The little alcove between the tub/shower and the wall that is 3’1” seems a bit useless given the size of the linen closet in the bath. Perhaps you could capture that as a closet for the office, turning the office into an “official” bedroom for later resale. Or, simply, storage for that space. The new wall could then be used for the heated towel rack. I appreciate your desire for a period appropriate bathroom, but a vanity with a counter would be more useful than two pedestal sinks. Perhaps a custom vanity that looks like a piece of craftsman furniture? A sideboard? With two sinks. And a soapstone countertop. Just a thought….