If you confess with your mouth the Lord Jesus and believe in your heart that God has raised Him from the dead, you will be saved. (Romans 10:9)
Make them all one-time effects so there is no need to set aside counters.
Asteroids: Make it asteroid pocket - all entering ships take 6x strength 1 attacks. Ships with point defense are immune.
Nebula: Explosive gas pocket - all entering ships are attacked once with a strength 8 attack.
Supernova: Pulsar blinds sensors - CAs with explore tech loose it upon exploring this hex (need to return to SY to "repair"). Other units entering are treated as Lost In Space.
Black Hole: Space-Time anomaly. Roll one die: 1-3 destroyed, 4-8 gain +1 movement immediately, 9-10 do not move next movement phase.
I love your take on this!
And yes, I forgot the Doomsday Machine.