I've never really been clear on this, but I've heard the blue mage spells deal more damage if they come from a monster that would intimidate it's target. Ex. Sprout Smack from a sapling would deal higher damage than normal if used on Tiger, Because Beasts are week to Plaintoids. I've ask other beastmasters in game, and our general consensus was that the only noticeable effect the strength's and weakness of mob types seems to be the chance of intimidation. I know SE added a merit ability to share the pet's affinity with a party, but most of the beastmasters I've played with found feral howl and beast affinity more important. Assuming intimidation is all beasts get out of this system, I'd kind of like to see it get some perks such as a notable damage modifier similar to that of piericing, blunt, slashing vs certain mobs.
This would GREATLY promote variety in the types of jug pets bst use in parties. I think most of us only carry 1-2 types of jugs. I know I prefer Lulush for damage and healing, And Yuly for TH and soloing, and frankly, it gets pretty boring. The others just don't seem worth lugging around. I'd like to use them but for lack of the pet's abilities compared to Lulush and Yuly, there just isn't a need.
It would also breathe new life into the long lost art of beastmaster soloing, as the fights would go by quicker with type vs type damage mods, be it in the new GoV camps, or in abysses if SE should decide to let us charm there.