Help me make a "simple" Sci-Fi RPG

It is very hard to make a simple RPG. I don't mean a rules lite game. I can do that easily. I mean an RPG that is simple to play. Most rules lite RPGs make things really hard on players (especially the GM) by giving a wide open world and no process for going through it.
With that in mind, I'm working on a game that is procedural, focused on combat, and the GM is purposely adversarial. I know that sounds awful but it's simple and I think it could be a fun experience if given the right constraints.
I need ideas though when it comes to the nitty gritty, I get stuck in style ruts and I see myself getting stuck with this. That's where you come in. We might not have ten thousand regulars that post here, but we are pretty diverse, so if there's a way to get me away from my comfort zone and out of a rut, let's do it.
On to the game. My working title is a bit B-movie, but that might have it's own charm. The game is based off a drawing my son did. I thought it was so freaking weird I might as well use it.
Star Eaters
We didn’t know why the stars were going out, but one by one they blinked and died. At first our scientist tried to find a an explanation that didn’t involve aliens. Eventually they resigned themselves to some kind of class 2 civilization that was using the stars as a power source. The truth was far worse.
The young star eaters expand out into the systems around their parent. If they don’t feed on a star, they never reach adulthood and eventually die. That means the young will never stop coming as long as the parent is alive or we still have our sun.
We don’t know what the parents look like, the closest one consumed Proxima Centauri thirty years ago and we did’t have a good way of getting there until we learned more about the star eaters.
Each child is different but most are hundreds of kilometers long. At first it took fleets of space ships to stop the star eaters until we found their weakness. Their hides are nearly impenetrable even by our largest fusion bombs. By entering their mouths and traveling deep down their digestive tract, small groups of fighters are able destroy an organ to stop them from feeding.
Our neighbor stars are still going out one by one and more and more children are coming for ours. They say in ten million years, all the stars in our galaxy will be dead. We have only one way to stop that. Each child has organs that can be harvested to power kill vehicles. Each star that goes out has an adult that must be killed to keep it’s children from spreading. The more stars go out, the faster more will go out.
The Resistance
Mechs
Brute force is the name of their game. Mechs are durable and do plenty of damage.
Orbs
These small self contained craft use technology developed from studying the star eaters. They have three modes. Only one can be charged at a time so choose wisely. Orbs can fire a plasma beam that is very powerful, they can create a nearly impenetrable plasma curtain or they can create plasma spheres that act as an active defense system.
Biohackers
A biohacker is able to alter the function of various organs in the star eater using chemicals or electrodes and change their behavior. They can also become temporarily invisible to the Star Eater’s defenses by altering their bio signatures.
Artificer
Team mates often need spare parts for repair and more weapons and ammunition. Artificers can also produce replacement body parts that Biohackers can use to heal with. Artificers can produce items that the team may need to circumvent some defenses.
With that in mind, I'm working on a game that is procedural, focused on combat, and the GM is purposely adversarial. I know that sounds awful but it's simple and I think it could be a fun experience if given the right constraints.
I need ideas though when it comes to the nitty gritty, I get stuck in style ruts and I see myself getting stuck with this. That's where you come in. We might not have ten thousand regulars that post here, but we are pretty diverse, so if there's a way to get me away from my comfort zone and out of a rut, let's do it.
On to the game. My working title is a bit B-movie, but that might have it's own charm. The game is based off a drawing my son did. I thought it was so freaking weird I might as well use it.
Star Eaters
We didn’t know why the stars were going out, but one by one they blinked and died. At first our scientist tried to find a an explanation that didn’t involve aliens. Eventually they resigned themselves to some kind of class 2 civilization that was using the stars as a power source. The truth was far worse.
The young star eaters expand out into the systems around their parent. If they don’t feed on a star, they never reach adulthood and eventually die. That means the young will never stop coming as long as the parent is alive or we still have our sun.
We don’t know what the parents look like, the closest one consumed Proxima Centauri thirty years ago and we did’t have a good way of getting there until we learned more about the star eaters.
Each child is different but most are hundreds of kilometers long. At first it took fleets of space ships to stop the star eaters until we found their weakness. Their hides are nearly impenetrable even by our largest fusion bombs. By entering their mouths and traveling deep down their digestive tract, small groups of fighters are able destroy an organ to stop them from feeding.
Our neighbor stars are still going out one by one and more and more children are coming for ours. They say in ten million years, all the stars in our galaxy will be dead. We have only one way to stop that. Each child has organs that can be harvested to power kill vehicles. Each star that goes out has an adult that must be killed to keep it’s children from spreading. The more stars go out, the faster more will go out.
The Resistance
Mechs
Brute force is the name of their game. Mechs are durable and do plenty of damage.
Orbs
These small self contained craft use technology developed from studying the star eaters. They have three modes. Only one can be charged at a time so choose wisely. Orbs can fire a plasma beam that is very powerful, they can create a nearly impenetrable plasma curtain or they can create plasma spheres that act as an active defense system.
Biohackers
A biohacker is able to alter the function of various organs in the star eater using chemicals or electrodes and change their behavior. They can also become temporarily invisible to the Star Eater’s defenses by altering their bio signatures.
Artificer
Team mates often need spare parts for repair and more weapons and ammunition. Artificers can also produce replacement body parts that Biohackers can use to heal with. Artificers can produce items that the team may need to circumvent some defenses.