I've posted an idea in the thread referenced above:
The main thing is that this should be decoupled from the batch size and become a separate setting – either instant_submit or even a number of maximum answers to keep (if set to 0, this would mean every answer is saved immediately). You could still combine it with a batch size of 1, which would have the effect you're looking for – but users could also send out larger batches while still having answers sent back instantly (e.g. to do single updates to the model or trigger something else on every update).
So this is definitely something I can implement for the next release.