I know this isn't a a popular opinion here, but sorry the truth is Robin to Nightwing was a step down, the most interesting thing about Nightwing will
always be that he was Robin to Batman.
Grayson's Robin identity will always have the most cachet; particularly Grayson's take (going back to the Golden age where he's the young ,devilmaycare, daredevil, solo taking on Zucco (his parents killers) and the mob, somersaulting, slingshoting and kicking mobsters (even the Joker) off city skyscrapers to their death! So much that Batman has to intervene to save them from Robin. This will always be the definitive version, who Batman recognized in himself, had to real in, and take under his wing, so he wouldn't become that.
DC has forever since been trying to retrieve that, with all these crap derivative "re-imaginings" of the character, so they can have the young version back, and new readers can tell themselves look how edgy Robin is now, with mostly (creepy clones) trying to imitate the original. LOL!
With an inherent ongoing sliding-time-scale being the lifeblood of comics characters and why they've lasted so long, (despite some fans here pretending aging them is the way to go) One of the worst moves DC did was aging this character to Nightwing, when the only update he needed was a costume, adding green/black leggings cape and full boots.
Which Neal Addam's pretty much came up with for Grayson anyway, and every "new" incarnation has shamelessly with out credit been appropriating since.
Lightning Lass to Light Lass didn't make much difference, more essential were costume upgrades. .
Name Speedy (and more importantly costume upgrade) to Arsenal wasn't bad.
Kid Flash (Wally) to Flash was pretty good, although completley riding on the epic tragedy and sacrifice of Barry Allen, by end had one exhausting story beat his fans repeat like a mantra, "I have to live up to Barry's legacy" which once played out, rendered the character completely uninteresting. Everything interesting he was came from Barry. (just don't tell them that)
I always thought back in Titans 1976, Malcolm Duncan, who was already a legit Titan, dawning the exo-skeleton suit and adding the Guardian armor, to become the New Guardian was bad ass!
I guess they thought Harper would be back, and wanted something more his own for Mal, hence Hornblower/Vox which honestly sucked.
I know YJ has explored it too, They should have Mal take this gear and name back for good.
Or if Harper has to have the name, just call him Defender or Sentinel.