Replay the battles, try to pick favorable areas and try to lose only the units that your inquisitor can resurrect. That's a lot to go around in hard and impossible, I know but... you have few options.
Another option is to try and restart the game and traverse greenwort, arlania, velarion and the swamp for good items and leadership flags whilie avoiding the fights. This is generally a good way to start a game.
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