[MrLobster]

All this is based on only one thing... Roids.

Basically having only one set of roids (roid belt in the galaxy).

Sectors
Each sector has a single planet, a roid belt (which stores all your roids), and a fixed set of moons around the planet (5 Max).

To colonize a moon, the moon has to moon base (Simple as clicking on a moon and then click create moon base).

Moons
Benefits from a moon are never as good as from the main planet (maybe 10% bonus). Also can only hold 10% of main planets maximum structures and are included in the maximum allowed structures.

1. Building of Structures so you can spread out the structures.
2. Additional Population.
3. Because of low gravity, a moon get a production bonus.

Combat
The sector fleet are always protecting all planets / moons / roidbelts in a sector.

Pods fire at the roid belt.

You could even include PDS, which could be spread out between all planets.