Like think about a stability ball those big ones where you can sit on it and then hop around in a direction and the ball would kind of bounce under you then come to a stop in the direction you moved in?
Couldn’t find a clear enough picture but something like this
Unless you’re trying to add a lot of unpredictability to movement, I wouldn’t use physics at all and just stick to animations. Otherwise, I’d consider using an align rotation constraint to keep the person from falling backwards. For moving forward, I’d consider using a method like ApplyImpulse on the ball, just angled upward towards the direction the player wants to move in.
You could use physics constraints like a BallSocketConstraint or a BodyPosition to keep the player on top of the ball while allowing movement. Then, apply a force or BodyVelocity to move the ball in the direction the player moves (WASD). For bouncing, detect when the ball touches the ground and apply an upward impulse.
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