[Kamog]

Moving planets will be interesting. If there's some enemy ships in your system, your planet may intercept them if they are on your orbital path. I guess that satellites, bases, and ships orbiting your planet will move with the planet, right?

Putting giant engines on a planet and moving it around will be fun but we'll need to put that kind of technology really high up on the engine tech tree. Imagine having a huge fleet of sphereworlds warping around the galaxy, wiping everything out. Or put engines on a black hole and move it into an enemy's system.

Maybe we can have star systems revolving around the galaxy, too. The systems near the galactic core will go around faster than the ones near the edge. Actually, the planets near the star should revolve faster than the outer ones, too. With binary and trinary systems, the stars should revolve around each other.