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Loyu – respect for the initiative :)
I suggest the following. Play mirrored matches, but without fully revealing the map. That is, at the beginning of the game, the red player saves the game at the beginning of their turn. The second game starts from the same save, but the players switch sides!
This adds extra tactical complexity. A partially known map, and known opponent's capabilities (which were previously your own) introduce unconventional twists to the usual randomness. The first game can continue until the last hero – the losing side benefits from prolonging the game to explore more of the map. But it is necessary to clearly define the moment when the first game ends, when it is no longer possible to move and explore the map.
In my opinion, fully revealing the save is not as interesting. It is much more interesting to set new goals for exploration (or counter-exploration) in the game, and even a losing game can be used to its full potential for a rematch.