Ah cool, glad to hear you got your experiment working! Also makes me happy to see that it's possible to extend the interface in such a complex way via Prodigy's scripting API 
I don't know off the top of my head how a DOMContentLoaded listener would behave inside another DOMContentLoaded listener but your interpretation definitely sounds reasonable. Btw, Prodigy also fires custom events you can listen to, including prodigymount. When that's fired, you know that the app has mounted and window.prodigy etc. are available. But not sure if this would make a difference here.