You made points that don't actually contend with anything I said. Again, the player, get to choose Johnny's ultimate fate. The fact that V is dying is relevant only as a tool to generate a sense of urgency. It's actually one of my primary gripes with the game, in so much as that urgency is only felt after certain missions with certain triggers, but that is a product of the open world game design more than a problem with the story itself. See, Johnny is already dead and even if he's not, even if that is the real Johnny in V's head, he's also dying just as soon as you get him out of you and 'Alt' absorbs him.
Now don't get me wrong, V is a primary protagonist in this story, and I can accept that the story is about BOTH V and Silverhand, but in the context of the experience I've had with Cyberpunk, which includes all the tabletop games from the 90s as well, I'm seeing it as Silverhand's final coup de grace. Remember, V is forced to take on Silverhand as much as Silverhand is forced into V, and whilst we, the player, don't really see the full narrative potential of that interaction play out while we're busy shooting up Scavs in Pacifica while chasing down errant VDB cyberpsycho netrunners and grinding out our 50 kills with Skippy, it is not an irrelevant interaction. The choices you have as a player do not represent a narrative arc for V, because that would require V to change as a person. They don't. Any changes that V has a minor shifts in opinion, at most, but there is no real arc for V. V's story is a simple "save yourself" one, the very core of any good cyberpunk story, but the actual character arc goes to Silverhand.
The story can absolutely be about both of them. But if it has to be about one or the other, it's Silverhand. V is just a passenger in that, the same way that Geralt of Rivia was always just a passenger of Ciri's story in The Witcher. Once again, many people make the mistake of thinking The Witcher is about Geralt, and whilst it does tell stories about Geralt, the primary narrative arc is about Ciri. Cyberpunk tells a story about V, sure, but the primary narrative arc is about Johnny Silverhand.
I agree with a lot of the points you're making but the suggestion that there's only ONE character arc (I really don't get this; there's several) and that the whole story is about Silverhand literally doesn't match up with the way the game is structured. That link shows you what all the main jobs are, which form the main story, and clearly V is the protagonist with their primary objective driving virtually all of them.
Where I agree is that Silverhand has a very well defined character arc compared to V (so does Panam, Judy, River and Kerry, for that matter). V's character arc doesn't really shift far from the landfill. You spend every main job from Act 2 onwards trying to find a cure and unless you went the Temperance path or ended things above Misty's.... you're still trying to find a cure :/ So, I totally agree it feels like a very unfinished arc compared to the other characters. It's very dissatisfying, but, nonetheless, that doesn't change the fact that her arc, regardless of the state it's in, literally forms the the main plot.
The only ending in which Silverhand's story feels like it takes precedence over V's is specifically in the Temperence ending, but that's it. Otherwise, V's story is primary all the way.