On the odd chance anyone else might find this useful:

File CBOY_nudist_bathShowerNoShoo.package : replacement semiglobals in group 0x7FE69E23:

   0x200A  Enter Shower
   0x200D  Enter Bath
   0x205A  Enter Shower - Bathtub Shower

All made nudist-aware: Sims otherwise willing to be naked in a room containing a shower or bathtub won't shoo other Sims out before making use of it.  (Doors into the room still get locked, though-- so if a Sim leaves, they may not be able to reenter.)