@ahojnnes : On further thought, I think they should be kept different. It is true that one would not use `keypoint_orb` without `descriptor_orb` but the reverse is not true. I made some tests on this scene object image pair(http://www.cs.ubc.ca/~lowe/keypoints/) and the results were not that great because oFAST has been chosen for speed and it does not return good enough features. One would use a better corner/feature detector combined with `descriptor_orb` if the task does not involve real-time processing.

For ORB, we can instead make a wrapper so that the redundancy(of computing image pyramids twice) can be removed. Your say?