This fixes your problem: https://www.mediafire.com/file/xd7jqmbmwwz2x6d/BodyImageAutoSwitcher_mod.zip/fil...
It's not great because it needs to replace a node script instead of letting the mod infrastructure extend it, but it's still probably better than modifying the game files directly.
In summary:
- Extend NODE_SLAVEMODULE since that's the nearest GUI node we have a handle to.
- Minimally replace the update method in SlaveBodyModule.
- Replace the node script at NODE_SLAVEMODULE/$SlaveBodyModule with the customized script.