Considering that the Calliope who was destined to defeat Lord English was a different one than Ours, and since the two mirror each other in a lot of ways, I can see how it'd be possible that LE is a different Caliborn as well

Mhmm! The biggest thing about this theory though, is that Lord English Caliborn has the Ring of Void for some reason, and he claims that he seemed surprised by the Kids appearing, and by ARquius all of sudden, which is weird because Caliborn is just SEEING that at that moment through one of the screens and saying how weird it is that he’s surprised… So it’d make sense.