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I think they could have also re-contexualized their Grandmaster/Anti-Monitor character if they ever wanted to explore the Multiverse further when they introduced Alan Scott. The giant robot Anti-Monitor could have been revealed as a harbinger of the real deal from Qward, which would have come into play with the whole Sinestro Corps storyline.
The reveal about Aya's true nature showed how they were able to keep peeling the onion with their characters. Just as Aya had a facet of Ion within her, the Giant Mecha Anti-Monitor could have revealed to have been a mere aspect of the true Anti-Monitor...which they could have revealed in the Blackest Night season.
I think you're all forgetting the one, true star of Green Lantern: The Animated Series