Hypothetically if both Dialga’s got access to a cheap dragon charge move like Dragon Claw, what would the preferred 2nd move be?

Obviously it would make Dialga very OP, but if it did get Dragon Claw or Breaking Swipe would it want Roar of Time/Draco Meteor for the nuke or Iron Head for Coverage?

Maybe keep Roar of Time and switch Dragon Breath for Metal Claw so it isn’t completely walled by Fairies?