Chrono Trigger apparently was supposed to have unique battle themes for every time period, I could see a remake using a theme like this for the post apocalyptic time period.
The pre-release version of Chrono Trigger had a remix of the battle theme that sounded like it occurred during the Prehistoric Era part of the game. It sort of gave off the impression that there would be similar battle themes for each of the eras, so it was a pity that idea never came to fruition in the full game. Perhaps you could make it happen.