For option 3, there should be 2 queues, 1 is SENT via SMS, and second SENT via DATA. As soon as the form is finalized, the form get queued into both queues. SMS should be sent immediately and the form should be released from this queue. But form should remain in data queue, unless it is sent via data and cleared afterwards.
This seems like a good idea. It's not what's currently planned but perhaps we should re-evaluate. I will make sure the Technical Steering Committee discusses this soon.
SMS should send some submission identifier along with data
This is something that's been left up to the form designer because it's hard to do well in a generic way. For example, in some forms, there may be a barcode that's scanned to get a unique identifier. That will identify the record and the form designer can include it in the SMS submission by providing a tag for it. In other forms, there may not be such a unique identifier and in that case the form designer can provide a tag for the instanceID and use that. The downside of the instanceID is that it's quite long so it's not included by default. Does that make sense to you?
Second, SMS should somehow include which question numbers are missing from SMS data (like Q5 if it has image, Q7 if it has audio/video, etc).
This also feels like something the form designer should control because it doesn't seem everyone will have the same needs. What I would do as a form designer to meet that requirement is add a calculate question with an SMS tag that has value T if an image was selected and F otherwise (or 1 and 0, or anything you want). Would that work for you?
By the way, I have worked on SMS technologies for over a decade (hence my enthusiasm for it!), so I would be happy to help in any design steps for fine-tuning SMS channel (like above) if you require.
That's fantastic! It would definitely be great to get your insights on some of the next wave of SMS features and any other requirements we may have missed.
You may want to read the original thread at Send submissions via SMS and see if you have any additional suggestions following that.