Expanding on this, I feel that people need to remember that Johnny's point of view on Soulkiller is painted by his life-experiences as a War Veteran and personal bias. He's a very troubled man, you can see this all throughout his past - so his view on Soulkiller should be taken with a pinch of salt and not the complete picture. When you get hit by it through Alt in Mikoshi, you literally do not even experience a thing any differently than you did experience things hours beforehand.
Alt even says that she's not really 'Alt' any more on this matter, but that is because she's an AI at that point in the game. She has no 'body', a floating entity within Cyberspace that is lacking emotion and passions and is essentially just protocols acting out a point in her life in defiance of Arasaka. This whole element is emphasized by how the Voodoo Boys require a pure, extracted memory from Johnny's Engram that Alt will recognize, because she will not recognize anything else—think of it as Game Coding in the C++ engine, certain things have to tick certain boxes in order to the code to operate properly, without hostility.
Yes, she is capable of developing further nuances and associated data within that AI of hers, but without a body, without the ability to accumulate human experience, emotion, and drive, she is not a 'Human' any more.
Johnny grows. Develops, within V - he experiences things, he shares the same neural pathways and body. He even states that for 50 years, he was locked in that moment of death, a prison, festering over the same memories and never actually able to do anything else - like a sensory deprived chamber. Before he ended up in V, he was cell-locked in that moment.
The game also questions at what point in life within the Cyberpunk universe do we lose our humanity? Think about that.
This is why I am of the opinion that the 'Going with Alt' ending is actually one of the worst ones. You're casting aside what makes a person a human, entirely.
You're certainly right about this, it's a lot more in-depth than it seems. And it fits the name of Soulkiller. Without a body, without those further developments, your soul will die. Just like it dies in real life when you don't expand yourself.
Regardless, I hope they expand on this.
Completely random, but I find it funny that Alt + V is a shortcut to view a file (Soul). And (control) Ctrl + Alt + V is smart copy and past command. Makes me wonder if they did that on purpose.