I've now been trying to use Spark as a pattern constructor and sound generator, so in practice, moving the "Song" construction into the DAW and out of Spark (i.e. "Host" button off).
Pattern .WAV drag'n'drop into ReCycle is a perfect tool chain for making REXs out of Spark built patterns.
Drag'n'dropping pattern .WAV into Live's "loop" slots works very well also.
The only issue I've encountered and wanted to make a notice of, is MIDI pattern exporting to DAW for DAW-based Song construction out of Spark made MIDI Bank patterns.
It works great *IF* we stick to Spark Pad mapping.
It won't work as expected if we're using General MIDI mapping or Custom (like I was in my tests).
So, this little issue could be ignored I guess, since Spark is supposed to work closely together with it's own controller, so, normally, one would keep using the Spark mapping, compatible with the mapping used on MIDI export, thus, compatible again when playing those MIDI clips back into Spark through the DAW.
But... if it's considered an important issue, being able to export MIDI patterns/banks while using alternate Pad mappings (non-Spark) as it looks like it is by looking at the current existing Preference options, then there's one option missing that would help with this:
"Pattern MIDI Export Drum map model" or maybe "Choose Drum map model for Midi Pattern Export".
And to help keep things as simple as possible, it should have an option like "same map model as Import" or something along these lines.
EDIT: oh, and also "same as map model for Pads" ...maybe this one's really the most useful in the scenario I described above.
Just a suggestion