Filing as a bug, rather than feature request, because the process appears to support it but doesn't.
Here's a patch which adds this functionality.
I'm noticing that nodes which didn't have any checkmarks in the original are coming through like "0,0,0,0,0..." While this isn't how the data should be formatted (it should just be empty), there appears to be no harm done, though I don't know how it works for fields outside of my use-case.
This one may still need more work. I'm not sure about it.