Simple idea: add an option in the align selection window to be able to mirror any of the 3 axiis.
for example if i'm snapping a helper to a symmetrical object's vertex and I want to do the same with another helper on the exact opposite side of the object, I'd like to be able to align the new helper to the original helper and but tell the align to the mirrored X value.
currently if I want to do this I have to align to the original helper and then add a '-' to the x coordinate value after the alignment. obviously if the mesh is low res and clear you can snap the second helper to the opposite sides vert much like the first helper, but on dense meshes it becomes difficult to find the exact same vert.
thanks!
