It is better to keep the discussion on the forum, as markups are very actively developed, we are still making many design decisions in these weeks, so it is good if we hear about user needs (to ensure we choose design options that make it easier to implement them in the future).
@sunderlandkyl is working on the new ROI (box, sphere, curved box) widget. For this, we will improve interaction handles, which currently only supports translation and rotation along the centerpoint, but will support additional handles (to edit ROI/slice intersection).
@RafaelPalomar is working on making the widgets customizable/extensible in extensions. It should make it easy to add a custom widget representation class in Python. Displaying an arrow at each markup point could be a custom widget representation.
Since we already have orientation as part of markups, displaying markups with an oriented widget should not be too hard to implement in Slice core either.
And there are also markups measurements, which we are improving and could be used to additional pieces of information in views.
So, just keep the discussion visible here on the forum and describe what you need - we are listening.