Sorry for any mistakes with details here, it's been a long time since I worked with pcf's and I can't do much experimenting myself because I had to move to linux.
Removing the renderer/children/initializers/emitters headers will work on pcf's that are loaded and remove it in sv_pure. I never looked into which one will cause the particle to stop existing, but just clearing all of them works. Iirc, item_fx.pcf doesn't even need preloading (and maybe some of the dedicated unusual effect pcf's, not sure), at least for some effects. It's the exception however, and from my basic testing I didn't find any other files like that.
iirc particle_manifest doesn't get preloaded. That'd be your main hope, since the particles folder is very much in the sv_pure blacklist, so it shouldn't work but might.
I never tried creating new particles by the name of what I want to remove into a pcf that works (for example, make a new particle in item_fx.pcf called "rockettrail" to override the actual rockettrail in another pcf, and make sure its headers are clear so it won't render. Assuming that rockettrail isn't already in item_fx.pcf, I forget). And again, being on linux doesn't really give me much of a chance to test that.