I spent way too long yesterday thinking about this, and it's actually harder than it looks. The animal metaphor aspect is so baked into 'Beastars' that you can't just drop Legoshi into any universe. You need a world with a similar kind of internal logic, or where the clash itself becomes the story.
One that clicked for me was the world of 'Blade Runner'. Think about it: Replicants are the ultimate 'predators' in a human society that fears them. Legoshi, struggling with his own predatory nature, meeting Roy Batty or K would be a fantastic mirror. The themes of identity, what it means to be 'real', and navigating a world that wants to kill you for what you are line up perfectly. You could have some amazing noir-style scenes of them talking on a rain-soaked rooftop.
Another weirdly good fit is 'The Witcher'. Geralt is a mutant, ostracized by humans and monsters alike. His relationship with the herbivore/carnivore dynamic is fascinating—he's a 'predator' who chooses not to be, a protector, but still viewed with fear. Him mentoring a young, confused Legoshi on how to live with that kind of burden writes itself. Plus, the gritty medieval setting would be a brutal but interesting shift from Cherryton's polished society.
Honestly, I'm less convinced by the obvious anime crossovers. Throwing him into 'My Hero Academia' feels too easy; the 'quirk' discrimination is there, but it loses the biological gut-punch of the original. The best crossovers use the setting to examine 'Beastars' themes from a new angle, not just for a fun fight scene.