Adding a field to existing form (with data) and updating it by API - good idea?

1. What is the issue? Please be detailed.
I have an existing dataset on Central which is relatively 'rich' (i.e. lots of fields) and want to integrate a geotrace that has been digitised subsequent to data collection. I thought it would be useful to have the data in a single space rather than having to associate data from different sources.

Enumerators collected GPS data of their route (attached to the form as a GPX file) and that has been edited to generate a better approximation (!) of the route on the ground. So I have WKT and can convert that to ODK-geotrace, and these records are matched to the UUID of the form submissions.

Data collection phase is nearly complete, but there are likely to be additional records trickle in over a period of months.

I am wondering about the value and implications of:

  • updating the form definition to add a geotrace column (probably read only so that new records don't come in with a random trace) therefore creating a new version of the form, which would obviously be distributed to enumerators.
  • using the API to update existing records to insert the trace data (and periodically updating new records when they arrive).

In my head this would allow access to the submissions from Central allowing the data manager(s) to see the trace, make any edits and allow export of the full dataset (or ODATA linkage when I work out how to do that).
At present I am holding one dataset in QGIS (desktop) and one on Central (minus the trace!) - I am sharing a web-map version of the QGIS data, but that can't be edited by a 3rd party.

My support questions are:

  1. Is this a good idea and worth the investment of time?
  2. Would I be better to create a new form (including the geotrace) and populate it via the API - it does have a nested repeat and I don't want to max-out my server space by duplicating all the images.

I know that this is close to Entities concept but we're not able to bulk upload entities yet (I 'only' have 500 records here, but 6000 geolocated images as nested repeats) - these records will probably become entities in a future iteration (this is the audit phase and we then need to think about managing!) - probably separating the records from the images as 2 datasets.

But I'd like to move forwards slightly without breaking anything (haha!) and let the data manager(s) get access to the data in an editable format (via Enketo, obviously) and maybe share data through ODATA

Feedback welcome... gulp.