Thanks for adding the functionality! It seems to work great. Partner Trainers really need an overhaul in general, but as you said, it's out of the scope of this plugin. This is still way better than spamming the difficulty variable on every NPC in the game.
Partner Trainer support would be awesome. They seem to scale once, but never again. It would be even better if it was separate from the rest of the scaling in the settings so you can only have Partner Trainers scale with you.