I don't think it can work as there's no ability to set a Z axis for the line of sight behavior (Or pretty much any existing functions).
I was messing around with basically firing a sprite from the camera to where the user clicks by means of the move to behavior and manually adjusting the z elevation of the sprite as it moved which can sort of work because collisions are detected. But ran into issues with regards to speed and the thing moving so fast it was going through the object being clicked on and not detected.
So my solution thus far is instead of having the behavior move the sprit is to create a loop based on the distance from the camera to the click location and iterating through moving the sprite 1 px at a time and checking for collision.
First test seemed to work but lots of tweaking is needed. But now I'm thinking "ok, so that could work for clicks but what about hovering?"
The mechanics of using this just seem so horribly inefficient. I really think the correct solution here is for the devs to actually code this simple functionality into the game engine.
Thanks for your suggestion though