Honest opinion here.
As cool as the idea is, this doesn't seem like the kind of project that can be properly made by a one-man team. I'd recommend decreasing the scope.
1. Scratch the RPG part. "Normal" rpgs are already severely troublesome to make, even with huge teams and budgets behind it.
2. Try to make a game where the better of your skills can shine. If you aren't good at writing, or never properly wrote before, don't try to make a game with loads of dialogue or deep lore. On the other hand, if you're good at making music, animations, etc, make sure those aspects will be used to properly convey the experience you want.
3. Don't, I repeat, don't feature creep. I say this because its too easy to commit this mistake when making space games. Do you need a futuristic cyberpunk city? If you do, do you need an entire futuristic cyberpunk city, or just a collection of areas will be enough for what you want? Whats the point of landing on a random place in the planet? Keep asking yourself questions like that to make sure you don't end up adding a bunch of pointless stuff that'll just increase your workload and waste the player's time.
4. Remember, simple and straightforward is better. Leave the ambitious stuff to the people with millionaire budgets and 400 men teams.
Some games i believe can serve as reference:
Original 2001 Deus Ex (of course)
VA-11 Hall-A
E.Y.E Divine cybermancy
No Man's Sky
Starbound
The Outer Wilds
The Outer Worlds (yup, both of them)
www.artstation.com
