Too much at once, toyhandle!
Let's put a pin in asteroids, comets, etc. for now and focus on just the Cosmic spaces.
I'll continue to say let's limit ourselves to two effects. I could maybe convinced to do something with height advantage if it were dynamic, but let's nail down the other two effects first and see whether or not we want to add anything after that.
Two effects are:
1. Movement based
2. Damage based
Let's try not to get too crazy complex with them. Maybe, for the sake of trying to test them, we should do it one at a time.
I think the movement based is a bit easier to tackle.
So we could try something like:
1. SPACE DRIFT: Figures without the Flying special power can only move from one Cosmic space to another in a straight line. If a figure without the Flying special power moves from one Cosmic space to another this way, they must continue moving in a straight line this way until either they are out of movement spaces for the turn or they move onto a different type of terrain.
(Unsure on that wording, but that's an initial stab at it).