I've played a couple of games like that and it was a pretty good fit, I think. Mission in Space: The Lost Colony was perhaps more influenced by Aliens, but the survival horror setting could have been just as suitable for SS.
In the style of games like Underrail or Fallout 2? Would it make sense since most actors on board are dead and games like these rely heavily on dialogue? Maybe a prequel or sequel? Pros? Cons? I am not hinting anything or are developing anything - just an idea.
I've played a couple of games like that and it was a pretty good fit, I think. Mission in Space: The Lost Colony was perhaps more influenced by Aliens, but the survival horror setting could have been just as suitable for SS.
Your question is a bit vague.
The System Shock universe doesn't only contain space installations where everyone is dead, there's a fair bit of backstory about what life is like on Earth and off-world colonies (hint: it's not great.)
Isomeric games aren't necessarily RPGs, though you seem to be implying you're talking about an RPG since you mention Fallout and Underrail and heavy dialogue?
One of the reasons that almost everyone is dead in System Shock is because it allowed LGS to avoid making dialogue systems, which they felt weren't very realistic or immersive. It's hard to make a believable NPC that you can interact with, unless they're dead. (As an aside, this is likely also why you almost never get to talk to anyone directly in the Thief series.)
There's no reason that science fiction survival horror can't work in third-person isomeric. I recently finished playing Aliens: Dark Descent, which does just that - a small group of marines on a desperate colony overrun with xenomorphs, where almost everyone is already dead. The game is rather good and I would recommend it, though it's real-time and quite stealth/action oriented, rather than being a turn-based RPG like you seemed to be talking about.
If you want to make a science fiction survival horror game, I'd rather go with being heavily inspired by System Shock rather than trying to use its universe. You'll have more creative freedom with your own setting, it wont be as jarring if your game doesn't fit into or compare to the beloved classics, and most importantly of all, you won't have to worry about infringing someone else's IP.
I assume we're talking about something System Shock inspired, i.e. post-disaster survival horror set in space where you can play as a hacker.
For me, the first-person perspective is essential to my enjoyment of SS1 and SS2. I can't imagine getting immersed to the same degree if they were 3rd person, let alone isometric. I enjoyed Fallout 2, but it was all about questing aka running around and talking to people. A different sort of game.
The first thing I thought of reading this title was Crusader: No Remorse, which also had the 0451 code and imm sim elements like being able to blow up doors. Guys, we need another Crusader game.
If you make it like the classic talkie board game Omega Virus (https://boardgamegeek.com/boardgame/3086/omega-virus) im so in. Its all about working together to subvert a rogue sentient virus, and your little guys move about a space station collecting the necessary tools and access codes while the virus man taunts and tries to kill you.