If you search for "costume" in Community Content, you'll find a number of examples that attach objects to the player, and often hide the player itself from view.
Since you mentioned a ball as one example, Roll 'Em is a bit of a special case. WaveParadigm has talked about what he did on the Core discord:
when the player joins I spawn a physics sphere, make their camera follow that sphere, use ability bindings and look direction to perform movement on the sphere, and have the sphere manually set the player's (who has Been set to Invisible and scale 0.1) position to some offset away from the ball
Collisions and all are handled because the object has physics