If you are asking how to add different motion blur per object here is a sketch in Compositor.

You would have to isolate (matte) the object and apply blur just on that. All depends how complex or where the object is placed in space, if there is something infront covering the object or so ...

(Cubes are moving the same speed.)

I wasn't sure about the Shutter Curve, but it seems like there can be achieved something ...

I'm not an experienced in Motion Blur, so I can be wrong :)

If you are asking how to add different motion blur per object here is a sketch in Compositor.

You would have to isolate (matte) the object and apply blur just on that. Here I used Cryptomatte. All depends how complex or where the object is placed in space, if there is something infront covering the object or so ...

(Cubes are moving the same speed ... Cube A Blur 4, Cube B Blur 2)

Proper way to combine it back is to use Z-combine node, but it gives me some crop on blur so I'm missing something here :)

I wasn't sure about the Shutter Curve, but it seems like there can be achieved something ...

I'm not an experienced in Motion Blur, so I can be wrong :)