It's not a unit. It's a formation. the rules for units do not apply to formations. Based on my interpretation, no one "unit" is casting the power twice. They don't hand the way to use this to your advantage on a silver platter, but that doesn't mean that that's not what was intended. I think it's possible the wording is intentionally vague. To me "may not cast until the end" means you go last. The end of a movie is still part of the movie, not the sequel. The end of a sporting event is the last two minutes, not the post-game show. Based on the wording of the rules it's an equally valid interpretation to yours. It might seem cheesy, but as has been said, no more so than any number of things that any number of formations can do in the game right now. Maybe they'll clarify in FAQ, if not, I don't see any fair and reasonable way to settle it other than rolling for it.