I haven't tested it, but I guess you could add an area2d as a child of your rigidbody2d and detect the collisions of the hits with that. (Signal onbody_entered)
Than you can do in the script of your rigidbody2d:
So that only the collider of the area2d gets the collisions.
EDIT: Maybe instead of disabling the regular collider, you could use collision layers.
For example, rigidbody2D - collisionshape2D and objects which should affect it’s trajectory on collision layer 1, rigidbody2D - area2D - collisionshape2D and the objects which cause your Hits but don‘t affect trajectory on collision layer 2.