A few ideas!

1st this is the most obvious one and the one definitely most requested from the community and that’s Shields!

2nd this is easiest to implement but idk if its very realistic and that’s Large Gyroscopes. They’d be useful for bigger ships and stop the issue of having to make like a plane with just gyroscopes

3rd is Energy Weapons! For this one, one cool thing that could be implemented is having like a huge railgun weapon, that requires energy not ammunition. It could recharge similar to a jump drive, just with a longer cool down

4th again realism, but I know some people love the idea of like an airtight shield grid for large hangers, that allows ships to fly freely in and out

5th this is easy but like just larger and more variety in Hangar Doors. Maybe one that is circular kind of like a missile silo hatch. Or maybe ones that are just gigantic

6th Flat and Wide Atmospheric thrusters. Really just like that. Thrusters that aren't that tall but are very flat and wide

7th I have no idea how this could work with the engine, but thrusters that automatically tilt. Think like how wheels turn but with thrusters, making it easier for players to use less thrusters. This can already be done with hinges but this would make it easier to access and more mainstream. Obviously this is very useful so maybe a hinge could be in the crafting recipes. Logistics wise itd have a grid around it where you cant place any blocks

Thanks for reading my thought dumb lol!