I thought about this a little bit a while ago, I didn't really concentrate on it much but I think the beset way would be to just have a function for each pattern, and then yeah, you would have the timed release, the interval would call like a createDrone(x,y,dir, etc..)
You would need to be able to clear the interval too, i've had problems with this, mainly with just not being able to reference the timer for whatever reason.
The other way would just have an animation, and you would just need to adjust any hitTests referencing the X, Y of the bullet and stuff for the hierarchies
That's all I can really think of