I had considered the possibility of using git (or at least some VCS) fetching the changes, extracting the diff, processing that and then merging. It's a possibility for sure but the work involved might be even more than rolling our own RESTful updater. Thanks for the thought.

We looked at sqitch for another project a while back. I think it can do data changes OK but it is seriously overkill for this particular task (and the dependency tree is on the heavy side too).