the physics debug view was not very good and it also messed up some dependency trees in the bullet implementation. It was introducing Spatials to the base physics objects which should not really need to know about anything but jME math. Furthermore the debug view showed only physics objects that were actually being used with spatials and controls, giving the impression that removing a spatial does remove the physics object as well (because its debug shape is not rendered anymore). Finally it used an ugly way to render the debug objects and it did not display a see-through wireframe like most debug views do.
All that has been cleaned up now The debug happens in a separate AppState that constructs a debug view directly from the PhysicsSpace data. So all objects that are in the physics space show up and I can even add things like display of forces and other things later easily..
For the user nothing much changes, PhysicsSpace.enableDebug(AssetManager) has been deprecated in favor of BulletAppState.enableDebug(boolean) which attaches the needed DebugAppState automatically but the old method still works. While I was at it I also made the PhysicsSpace avoid double-adding/removing mistakes by the user by checking if the object was added already.