This is a very interesting proposal. While I have the Celestial Nighthawk, I have yet to actually level it up and test it out, so I have little experience with the armor piece thus far. The Celestial Nighthawk certainly has a lot of potential, but it requires much more coordination and effort to take down Crota with Nighthawks than with Ghorns. This is partially due to the Nighthawk being very situational and class-specific, rather than Ghorn, which can not only be used by any person of any class, but also doesn't require a super to fire. I would say that the Celestial Nighthawk will never fully inherit Gjallarhorn's legacy. It's effective, but it's also just too much work for people to bother with.