b) Secondly, for constructing diagrams, one often needs the same angle in several places - perhaps at known rotations with respect to an initial setting (e.g. force diagrams in physics).  It would be nice, once set, to be able to rotate the compass be some degrees (or radians, etc.).  This might be done with a second readout window below the angle readout.  You could enter the rotation angle in the readout (as in (a) above).  And/or perhaps you could rotate the compass by selecting a rotate handle and pulling up or down.  

I use the product (& calipers) a lot and am happy with it.  Hope it continues to be improved.