I have been playing with this also and may have come up with a goofy solution.
First you create a light boom, set your spacing, rotate the 3D portion into vertical. In Top/Plan view, convert it into a Lighting Position.
Import the lights you wish to use.
Then duplicate the lights you wish to use and edit each of the duplicates 2D components.
I.E.
The top light is a 26° ETC - leave it as is.
The second light down is a 26° - move the 2D component down the distance of your ladder spacing - if your ladders are on 2' centres move it down Y -2'
The third light down is a 36° ETC - move the 2D component down -4'
The fourth light down is a 36° ETC - move the 2D component down -6'
Go to your top plan view and position the modified ETC Symbols in order with the insert position all at the same point as the top/first fixture. Notice that the 2D symbols are offset 2', 4' or 6' - nicely inline for viewing.
Now go to a ISO 3D view and drag each 3D light over to the appropriate rung - find the insert point at the centre of the clamp and use the snaps to centre it on the centre of each rung.
Go back to 2D view and notice that the 2D components are still in place - Beauty!
You can select the light object and change the Z and the lights move with it.
This I like - now i can move my scenery around in 3D view and not have it run over a bunch of lights lying flat on the floor!
I haven't played with duplicating/mirroring the ladders but that will be my next experiment.
If I always use the same ladder spacing, then I will save the duplicated/converted symbols as Favourites.
Cheers!
MNP