How about try this way:
fristly create a layer with Particle Playground effect,contral the “scale” of the particles by “scpersistent property mapper” with a map.After that you can imitate a z-depth movement.
but the problem is that all the particles will look at the camera.if you wanted them to look at the centre of the Particle Playground,I have no idea about it..
By the way,it seems that the trapcode Particular plugin can make a better result,try this plugin if possible.