Well...here's a rather different idea.

It's based on:

--small kids who grow to be adolescents;

--empty nesters using the house when the kids have left;

--attempting to sell the house when it's time to downsize

Build two, separate, hall oriented bathrooms, each with a space with two lavatories, and another space with a WC and tub/shower. Don't forget a linen closet for each.