Brainstorming on monster training

In revisiting Pokémon Concierge...and thinking more about monsters in this "Monstrous6" set of rules I've somehow managed to not get distracted away from (despite that being my ADHDGMO*)...I've realized how little rules space has ever been devoted to mediating the interactions between player characters and monsters in pretty much any tabletop RPG I've ever played.

I guess the earliest application of this idea would be the monster Reaction Table introduced in 1974's original Dungeons & Dragons and carried through at least the full run of "old school" D&D rules.  Keith Hann, over at the blog Simulacrum: Exploring OSR Design, put together a nice overview of its changes through the editions.  The classic D&D approach is pretty...broad, I guess.  There's a lot for the DM to process and rule on.

In more modern editions of D&D (3rd forward), are there even official Reaction Tables to be used?  Seems to me that the closest analogue would probably be the use of a skill like Animal Handling (or, depending upon the monster, maybe Insight or Persuasion).  Even with these, it isn't clear how difficult to set a check.  Maybe there are just too many factors to take into account...the specific circumstances, the creature's intelligence, its history of interaction with PC-type beings, the intentions of the PCs, etc.  It might just not be worth it trying to nail down a precise procedure for "handling" a monster when that could have so many different looks.

Personally, I like what we see in West End Games' Star Wars Miniatures Battles: the Orneriness Code (which I have started to implement as Handling Difficulty).  I'm pretty sure I'll continue on this path.  I just have to figure out some pretty basic questions around it.  Like...who do I give this score to?  Is it just beings that lack intelligence of a human scale and variety?  What about something as smart (in a human way) as a chimpanzee, for whom the terms handling and training could even be interpreted as a bit insulting?  Surely Pokémon should get one (that's part of what prompted this post)...but the meaning of "handling" seems very different for a Mewtwo compared to, say, a Growlithe.

Images from Bulbapedia

I guess I need to do some thinking on this.  I don't doubt that there's going to be a great deal of DM fiat involved, and that's okay.  I dunno, is there something I'm missing here that needs to be taken into account?  Have I somehow, in my years of roleplaying, managed to avoid something crucial to inform my approach with this?

At any rate, here's Psyduck's evolved form, Golduck...who must be just a little more difficult to handle than its younger self, since as we all know, most Pokémon get tougher and angrier as they evolve...

Golduck

Also from Bulbapedia

5' 7" (1.7 m), 168.9 lbs (76.6 kg), Scale: --

Handling Difficulty (wild): 9

20 HP, 11 Defense

Movement: Swims at 3x walking speed

Type: Mind, Water

Weakness: Electric, Mind

Strength 2

Dexterity 3

Knowledge 1

Presence 3

Skills: Swim +6, Psychic Powers +3, Toughness +2

Attack: Headache (mental attack, 1D6 Mind damage; when hit, the target must make a Presence save or lose their next action) or 2x Claws (1D6 Slashing damage)

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* The G is for gamer.  You probably already know what ADHD and MO stand for.  It only seemed appropriate to initialize the whole thing...