What I'd really like in addition to the potential "visible range multiplier" for nebulas ('1' could be default, something greater than this number would increase the range, while a decimal would make a nasty, soupy nebula...) would be a "wave" or cloud effect. Basically, this would be a variable-density nebula. Even better, you could have one that would "move" - packets of the thicker stuff would drift about the thinner stuff... add this to stormy, red nebulas for epic awesome... Or, just have everything fixed while still having the variable density stuff.
I'd like to think you could do this as FS has a grid-like coordinate system. By almost "procedurally" producing denser pockets at algorithmically-determined distances, you could do a lot of neat things. Heck, this would be an AMAZING way of making clouds and fog for atmospheric mods. The wave effect would simply mean that the mass would move at a desired velocity... If you could have various sets of "dense pockets" moving at different speeds in different directions, you could make a truly fierce "swirling" effect...
And next, if you like my musings on this matter, would be the density by distance/altitude. Basically, set a desired standard or custom plane and "altitude" in FRED as the center point, apply the nebula density and direction in respect to the plane's normal, and you're good to go. Thus, everything below the plane would get denser (or less dense, depending on the settings) and everything above it would become the opposite. This would be good for atmospheric fog or a mission in which you're fighting in the upper atmosphere of a gas giant. Diaspora would be all over that one...
Last, the ability to use several different nebula types at once in a mission would be the icing on the cake. You could create environments that would just kick bumcakes in every concievable fashion... Heck, even just having a user-defined nebula "box" (similar to asteroid fields) would be great...
