Anyone see this?

[Kaworu, the Fifth Child]

DD: Mishra vs Urza? Anyone see this being a thing? Yeah, I want it.
Though they'd have to make a new Mishra card because his current one is combo oriented, which I don't think they'd do for a DD.

[Remillo]

Well, there's Phyrexia v the Coalition, which is sort of the same thing, just many thousands of years later.  The problem is that both the decks would be pretty much the same: Artifact Aggro.  Except Urza would be stuck with Ornithopters and Mishra would have Dragon Engines...  At least from a story prospective.

Also, Urza never actually got a card.  And they don't introduce new cards in Duel Decks ('New' cards are always just previews for the next set).

[Kaworu, the Fifth Child]

Well, {Blind Seer} says otherwise.
But I guess your right, though they could probably do something to make them different.