Thats pretty much what I am setting up, except I'm trying to get a bit fancier.

The tricky thing is to make this a reoccuring event, and not only make it dependent on a turn no, but also whether certain provinces are held by certain factions, such as "If province 1 and province two held by seleucid (romani and province 3 held by germans then spawn these two stacks at these locations every 30 turns"

IF I could randomize the spawn to occur with greater likelihood that would be even better, but that might takes some interesting scripting?

Is there anything in the main script which does something similar that I could just reinterperet?