HP, LP, trasnient analysis, right from ReaScript... That's one the most advanced audio analysis ReaScript :P
For the task, I would have used
GrooveExtractor Lite - LeSound by AudioGaming. Maybe you can take some inspiration from it.
But I'm really curious about how far you could go with a ReaScript solution.
What could be the benefit against GrooveExtractor ?
impressive job so far