Depending on where the hotspot is, the pink box should always have a greater y than the brown on when they are overlapping.
Actually I did consider this. But here's the catch: It's a rotating layout. I'm actually thinking of inserting a decoy sprite to be used as the relative 'higher Y' that keeps its position relative to the viewport.
I'll have to do some tests.
Also I forgot there's a 3rd case I just thought of last night:
For this case I'm thinking of put Tilemap and BOX_METAL inside a family (if C2 allows) and replace the:
overlapping TM at offset with
overlapping SOLID_FAMILY at offset.
Now hypothetically using the hotspot method it should work but I'm anticipating a whole other set of problems.