You could just watch the livestream to see what the other team does. How does that help? There will always be some ways to spy.
Well yeah that's kind of my point. We don't want to implement a DRM style solution that hurts the people who just want to spectate as much as spies as it will function much like DRM. Spies will still be spying (i.e. pirates get games before legit consumers) except with some of the ideas honest spectators would have to jump through hoops or not be allowed in at all (similar to paying customers getting hit by DRM harder than pirates ever will).
Spiers gonna spy, they will find a way, whatever solution intended to prevent ghosting needs to keep in mind that we're trying to limit the effectiveness of ghosting, not push all spectators out of matches (at least i think, maybe spectators
are unwelcome).