What about instead of having an arc measured in degrees, have a curved line measured in (insert measurement here) length? In the case of an omni-shield, the line would just move with the midpoint lined up between the mouse cursor and the center point of the ship/shield projector along an invisible predetermined "track" that stretches around the whole ship. This could handle the issue of varying shield raising speed depending on the position of where the shield is raised relative to the curve angle, and having an arc that needs to take special calculations into consideration for an ellipse. Instead of "Shield Arc", the display would say something like "Protection Coverage" with the number in a percentage of active shield length compared to the total length of the previously mentioned "track." This would help modders who like making long, skinny ships, but don't like the shield size and A.I. issues that come with them.
