Consider giving FParticleSystem a "global" flag.

[MattRix]

For some particles, the desired behavior is for the particles to not exist in their container but to kind of exist where they were created, even if their container moves... This can already be achieved pretty easily by the just putting the particle system on a higher layer above everything, but it might be nice to have an "myFParticleSystem.isGlobal = true" type of flag.