I think the best solution would be to have a toggle-able Count-In option on a per-song basis (set via BBManager) for, well, adding a one extra bar of a metronome count-in. Count-In would take precedence before Intro kicks in. BBManager will allow you to add (or remove) a song Intro, and set Count-In for a song independently.
In order to be able to manipulate this behavior while playing on stage, the pedal should provide two separate settings:
Play Intro: (will help to hack out the intro from songs)
- Use Song Info (will play intro for songs that have one)
- Force No Intro
Count-In: (will help override BBManager setting while playing via the pedal)
- Use Song Info (play count-in only for songs that have Count-In enabled via BBManager)
- Always Play (will play count-in for all songs no matter if they have Count-In enabled)
- Never Play (will play count-in for no songs at all no matter if they have Count-In enabled)
I’d also make these two settings session-based, so that they default to Use Song Info every time you power cycle the pedal.