Ask HN: How to model interplanetary light delays in a game?

This is purely a thought exercise, I'm not actually writing a game. I'm not a good coder and was wondering how this situation would be simulated. I've taken this from a good book series by Jack Campbell called The Lost Fleet.

You have a star system. Star, several rocky planets, couple of gas giants, etc etc.

Warship fleet A (200 ships) jumps in at a fixed point on one edge of the system. Fleet B (250 ships) location is on the opposite side of the system. Both locations are about 4 light hours from the star, and about 6 light hours from each other.

The light from your ships won't reach the enemy for another 6 hours. You start to approach the enemy fleet. After 6 hours they see your arrival, and start traveling towards you. You don't see the light from their movement until it has reached you. The light delay gets smaller and smaller as you approach. You can travel at a maximum of 0.4c but you can't target enemy ships unless your relative speed is less than 0.2c due to relativistic effects.

Before you enter weapons range, you try to arrange and maneuver your fleet such that it will cause the most damage to the enemy, without taking lots of damage yourself. Ships take about a second to pivot, so if you can maneuver just before contact, the enemy won't have time to react. Time to fire weapons at such high velocity is just fractions of a second, no human input is practical at that speed so targets are set up beforehand. It's a poker game, trying to guess what the enemy will do, and counter it while making sure they don't counter your attacks.

How do you model such a system? Each ship would need to be modeled, their velocity, position, armour/shields, etc etc. Mainly I'm interested in how the light delays would be tackled: would it be far too complex or can it be done? How would one player's view be constructed, would you have light propagation from every ship?