Optimize mobile game with lot of Rigidbodies (Collisions)

I'm currently working on a mobile game like Crowd City.

https://www.youtube.com/watch?v=6q5DVTbyH_c

The Gameplay is working well but the scene can contains a lot of instances of characters. I'm using a Batched Optimized SkinnedMeshRenderer script in my game. So I can display 1000 characters in 60FPS but the physics alorithms can slow down the game. https://www.youtube.com/watch?v=_GGVlzAcWgA

The 1000 of Rigidbodies reduce the framerate.

I would like to optimize the game to export a mobile game. Find the best configuration to build the best optimized experience.

The characters should collide with them and with buildings. (Rectangle shapes at least)

I already tried to use Phycis.OverlapSphere to avoid Rigidbody component but it's quite hard to resolve all collisions mathematically to get a good result.

Any tips?

Thanks.!

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