Separate particle systems rendered together with a single sorting mode?

Is it possible to have two particle systems that sort based on age/distance together? It seems that (at least in 2D) a particle system can only have all of its particles rendered above something (such as another particle system), or below it (which might be a bug?). This means that if I have two particle systems next to each other (such as rockets of a spaceship), one of the particle systems' particles will always be on top of the other particles, and the other always underneath, and any other attempts will result in z-fighting. Can I in some way have it as if the particles of both particle systems were combined into rendering as one, so that the particles can be sorted (by distance or age), without one of the particle systems always being rendered above the other, and vice versa?