As someone who cried when Junkie left, I'm totally onboard to bring back THE Batman theme. The theme from my childhood. I think at the right kind of badass moment, hearing that theme could be a crowd cheering moment. Imagine a scene where Batman swoops down from the shadows and kicks some Parademon ass and that theme is blaring on the speakers. Plus, like another poster said story-wise it works. While Junkie's theme was cool, it was definitely a much more menacing and brooding Batman theme to reflect the mind state Batman was in during that movie. Now, Bruce is back to his old self, he is THE BATMAN again and I think bringing back the classic theme is appropriate.
That said, there will be Hell to pay if the MoS has been discarded and is not used when Superman sweeps in to save the day.