> It appears that the one important event that I can't directly schedule is a tempo change. [...] It would be nice if I could just schedule this event directly in the sequencer when needed.
At the moment one needs to use a callback event, yes. However, thinking about it again, I do see a need for a dedicated FLUID_SEQ_SCALE event as well. I'll add one.
> This would result in a note-on event scheduled with the same time-marking as the tempo change. Will that be OK?
Tom