I think it would be nice to have the TrackBall orbit other than the just well present TurnTable orbit.
Justification
it is useful when painting for being able to rotate the view orientation in a way to match a good position from where to paint certain strokes, and even to being able to visualize in a more specific and precise way the mesh.
Implementation Details
it should be a button in the preferences or a drop-down, and it would also help to have a customizable shortcut in a way to fast switch between the two orientation system
Reference
blender examples:
