ok, I just figured how stupidly easy it was to do them

with some sacrifices, it can even be done w/o the SCP, but the sacrifices are annoying, that's why I post it here for you to judge.
ok, how to make a localized nebula:
1) create the smallest mesh you can and pof it, assign the invisible texture to it.
2) pick a species to sacrify...
3) replace the engine glow pcx of this specie with a nebula poof of your choice
4) on your previously created pof, create an engine glow.
5) make various copies of that pof, giving them the names of all the asteroids pof of a given color.
6) create a dense ( or not, you can use large engine glows, after all, might even look better actually ) asteroid field in fred.
voila!
now, the flaws:
-I don't remember, so I assume it's not there:
there's no tbl entries for the asteroids used in the asteroid field, just one for the lone roid. so you can't assign the no collision transparent tag. you'll bump stupidly against space dust, and destroy clouds if you shoot in it
-glows don't show from every direction, so you'll need 9 glows per roid. IIRC, tho, Bob changed that for the SCP exe?
-well, you sacrify a species, it's annoying...
-you also sacrify a roid field type.
-the engine glows flicker.
-that's it!
Thoughts, anybody? ( and anybody who wana try? I must confess I didn't, it's all theory

- but it most likely works, can't see why it wouldn't ).