We have since figured out a way to do this: Turns out there is an API in the version we're using and with a bit of poking around we figured out how to use the API. So what we're doing is simply running a script once, that fetches all data points, maps the old to the new device number and writes back the changed data point information.

This is good because we can reuse the general structure of that script to perform other bulk updates, like the template update, and can avoid the interface, which is painful to use over a mobile connection.