i am under the impression that a jutsu lvl has to do with chakra control and execution. wich is why super high lvl jutsu's are hard for sharingan to copy. unless the sharingan user has the required genius to comprehend what is his/her eyes are seeing. not only comprehend but have the ctrol of their body and chakra to perform it at the precision needed. I believe that the rasegan could easily be copy by the hyuga clan. not so much by other who have not strained their bodies to manipulate chakra from chakra holes. i tihnk the the speed and power requiments of the rasegan are what make it such a high lvl jutsu because of the chakra control required to pull it off. the exact reason why Naruto has to use two hands to do at his current lvl.