Well, work today was utter murder.  Still, I'm home now, and have had several hours to pore over the Stronghold Builder's Guidebook for ideas.  I'm too tired to finalize anything at the moment, but I am thinking overall that Torahime isn't really the type to need much more than the basics for living comfortably and training within the castle walls.  So any leftover stronghold spaces out of the 20 allotted to her could either be directed towards castle defenses, or perhaps towards creating a nice hotspring/bath with healing properties for all the Archfiends to enjoy...