Okay i said this idea before in the "cluster bomb" post but I believe it can be done.
How about having a weapon detonate at a certain time/distance/whatever and spawn a determinable number of another weapon, which acts as the submunition.
The submunition could be defined as and even used as a separate weapon in a plugin.
Here's my design for my cluster bomb again:
Cluster Bomb = turreted dumbfire submunitioning rocketflak
Shield damage: 4 (comes out to 5)
Hull damage: 4 (comes out to 5
Submunition type+#: 4 Cluster babies
Cluster Baby = a homing missile that homes in on your target automaticaly but only comes in cluster bomb form.