I've replied to another thread regarding this by another member.
I agree it would be good, although messy. The pattern format used by the BSP sorta means importing a regular .mid file won't be as straight forward as importing a .mid file to a full-blown high res multi-track MIDI sequencer. Max pattern is 64 steps @ 8ppqn, swing and note shift not withstanding (my M1 uses a 24ppqn resolution). We'd need to set what step division we are importing to, then how many patterns to split the track into.
All that said, if it could happen, it would make the BSP a great remix tool.