Unless there was an update I’m missing (and I would love to hear about an extension 3 !), I don’t think LT supports python right now. I think I read it also lacks support for file referencing, which could pose an additional problem for the ART tool.
On a different topic, how on earth do you go about selecting/moving leaf joints at the skeleton placement stage? 
I can only see preview bones for them - and changes to those don’t ‘stick’.
//solved my own problem, but for anyone else wondering: leaf joints can be selected in the ART tool’s internal outliner!