There isn't much of a way to mod the AI.
You can try decreasing the aggression values for aliens, which will make them less likely to charge out and more likely to hang out and wait for you.
You can change the intelligence of aliens, which defines how many turns they will remember where you are (and remembering that you are waiting at the entrance might make them not want to come out after you killed the first alien walking out)
Otherwise, that's it. And as was said above, try Sneaky AI in the options, that makes aliens less likely to expose themselves.
Frankly, the tactic of "press End Turn until all aliens have come out" makes the game so boring I never tried to use it. Breaching is where the thrill is, I don't know why you would deprive yourself of that.