Inventory2/player/Player.cs

public partial class Player : CharacterBody3D
{
	public MovementController  Movement  { get; private set; }
	public CameraController    Camera    { get; private set; }
	public AnimationController Animation { get; private set; }
	public PickupController    Pickup    { get; private set; }

	public override void _Ready()
	{
		Movement  = GetNode<MovementController>("MovementController");
		Camera    = GetNode<CameraController>("CameraController");
		Animation = GetNode<AnimationController>("AnimationController");
		Pickup    = GetNode<PickupController>("PickupController");

		foreach (var child in GetChildren())
			if (child is IInitalizable<Player> init)
				init.Initialize(this);
	}
}

public interface IInitalizable<T>
{
	void Initialize(T param);
}