[LordOfPixels]

Is there a plugin that allows admins to attach particles systems to players via a command?

[LordOfPixels]

Decide to make one myself.
Using the command sm_attachparticle <userid|name> <1/0> you can attach a particle system using one of the premade particles systems from List of CS:GO Particles.
It defaults to ambient_smokestack but you can change the type using the ConVar sm_attachparticle_type <particle>.