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Ok, first of all, tell us precisely what you want... Because you arent clear
If you were reading carefully, it is a strategy for comps for an RPG, so its more interesting, also he can't PRECISELY what he wants because he wants some ideas FOR the combat strategy..
On another note:
I could trigger it, not that I positively will, but use Expansion Zerg AI Insane(or protoss or terran depending on your RPG) and make hatcheries with mins and other buildings and make the building costs at near none and time to real low, so, the there will be different armies attacking you at different times.