BandHelper can't play MIDI files. This is on my wish list and I'll add a vote for you.
Add a vote for me too, and I'd use this for the following use case:
We create backing tracks in a DAW that are ultimately exported as .m4a files for playback in Bandhelper as Recordings.
We also send MIDI patch changes (e.g., guitar patches, vocal fx, etc.) synchronized with the backing tracks. These are added as Automation Events in Bandhelper by manually recording them while listening to Bandhelper play the backing track.
A preferred alternative would be to build these patch changes into the source DAW file and once the audio Recording is exported, also export a simple companion MIDI file with just the patch changes. Thus it would be much easier to position (and edit, if necessary) the MIDI patch changes in sync with the audio within the DAW, rather than manually recording them as automation events.
(We don't automate lighting yet, but if we did this would also be my preferred way to do that as well!)
This presumes an option to start MIDI file playback synchronous with Recording playback during performance.