The ability to align 2D/3D reference files to abstract angles. Especially for 3D where the current option to rotate is limiting when the angles are abstract on xy, xz & yz planes
I think you can set the Treat as element attribute in the Ref dialog which will allow you to use the Mstn rotate element tool. Would this do the trick for you? Not sure how you would key in out of plane rotations.
One way is to use in put an ACS. I think that this now being planned