Glass block corners on interior rooms

Support columns that are framed up and wires/mechanicals running inside them

All in one bathroom: one drain for entire bathroom, perhaps open shower, or just a small threshold for entry into shower

Interior windows and translucent walls, for example a translucent wall where the pantry's going to go and use open shelving for pantry so light still comes through into stairwell

Smaller pipes for plumbing so hot water gets to tap faster

Build cabinet under sink to be one or two inches shallower than the other cabinets to allow for ample knee/foot space. (like mom's in cambridge)