Snipes McKinley

I've been trying to find a way to spawn (ideally) different types of fire support on different smoke grenades. The idea is that when a specific colour of smoke grenade is thrown or fired from a launcher, after a short time ordnance will hit the area near the smoke. For example, Red Smoke would spawn a barrage of mortar shells on the smoke grenade's position after a short delay. Orange Smoke would spawn a small artillery barrage, etc. I am unsure where to even begin with this, or if such a thing is possible/practical. I got the idea from the old 'Mercenaries' series from Pandemic Studios - if anyone has played them then you understand what I'm going for.

I have searched around for days trying to figure this out, but nothing I have seen and tried has worked. What I am trying to do is this - When all units of a specific type are killed within an area, I want more units of that type to be spawned at a specific location after a set amount of time. I have a feeling the answer is a simple one, but I cannot figure it out. A more detailed explanation; I am attempting to spawn three 'Stalker' enemies from Devourerking's Necroplague Mutants mod in a location, after a set amount of time, and only if no other Stalker enemies are present in a designated area. Any help would be greatly appreciated.