Graphically these things look GREAT! The limitation in them I like that you lose sensor range. But could it be possible to extend this to the fact, if you are not in the nebula that you cannot see everything through the nebula and all around the nebula. It should be block for sensors outside the nebula itself. (Kind of a line of sight problem)
Treat the nebula like a sensor fog and give a line of sight that you cannot see through the nebula, only 1 layer range from outside. Thus, one could hide ships in these nebulae or dust clouds, or a star-base hidden in them.
I think this will bring in some strategic depth to the game.