Now that Halion 6.4 is out you could try it again to see if it still crashes when loading layers.
I have to discard the option to load layers, because there is a layer that always has to be available (it is the one of the script that you made of importing sampler).
Play note function has optional arguments. You can choose which layer or zone should receive the midi message.
if I can understand this a bit because as I said my knowledge of programming are bad, bad 
Does this function send midi to the selected layer?
function onNote (event)
playNote (event.note, event.velocity, -1, layers [LayerSelect])
end
Now I have to do another function that sets the layer midi mute parameter to “on” in all layers except the selected one, right? or I just have no idea