Can any program change the global gain of an MP3 in increments that are smaller than 1.5dB? I don't want to start a discussion on the merits of this. I only want to know if there are any programs that can do it.

I know I can do this with the -scale function, but that's not what I'm looking for.

I believe this a limitation of the format, and so therefore, no it can't be done. Not without reencoding.