Specifically I'd like to write an application that allows pattern and track information to be uploaded to a sequencer via its USB connection. That way If I have something in a DAW I can transfer it to the synth's sequencer w/o having to recreate it individually on different unit's interfaces.
This isn't really a matter of 'hacking'. Maybe the sequencer allows you to load playback data, probably as a MID file. Maybe this can be done as SysEx data over a MIDI link, which usually means a MIDI-over-USB connection these days. If the facility exists, it will be documented. If it doesn't, there isn't much you can do about it, short of pulling the ROMs out of the synth then reverse-engineering and re-writing its operating system.