You might try using characters rather than objects.
Can the objects go at fixed places or anywhere? If the former, you can make the NPCs avoid those places regardless of whether an object is there.
For the PC, you can split the room in half and use walkable 1-16 in the left half as well as in the right half, thus giving you 32 walkable areas; make the left half of the room region#1 and the right half region#2, and if the player steps on region #1 set the walkables as appropriate for the left half of the room. And vice versa.
Can the objects go at fixed places or anywhere? If the former, you can make the NPCs avoid those places regardless of whether an object is there.
For the PC, you can split the room in half and use walkable 1-16 in the left half as well as in the right half, thus giving you 32 walkable areas; make the left half of the room region#1 and the right half region#2, and if the player steps on region #1 set the walkables as appropriate for the left half of the room. And vice versa.