I think I would relate Slaneesh more with Futuristic Rave/Dark Electro etc and other stuff where drug usage is common compared to Heavy metal which would be more of Khorne's domain.
In any case, your story sounds interesting. Do you have a special like for Adeptus Arbites?
My biggest nerd crush is on the Sisters, but Arbites don't have a lot of fiction which makes it ripe for the picking with new stories. At least that's my thought anyways.
And metal has had LOTS of drug abuse by performers over the years. Cocaine being a popular go to back in the day too. Also it's got more kick ass guitar solos to make your ears bleed and skull melt.