JASS Theory

Say I wanted to create a sort of egg. It is a "building" that is built by another building(this case, dragon roost). The egg produces units. However, I want the egg to be destroyed after a single unit is finished producing, a lot like the Zerg eggs in SC. This isn't possible through ability or property changes, but I'm thinking it could be possible in JASS. I'm making a TC, so I want this to be a "default" type of thing, not map dependent, so it'd be in Blizzard.j. How could I go about doing this? Is there a way to set up a function to detect and handle when a building has produced a single unit and then remove the building(egg) every time, even in melee?

Heck, this could be a build order thing I could put in undead.ai(race being converted), I just don't know.

Any ideas?