The main problem with the existing batches is the stability and maintainability of the pipelines. That is because the batches had to use different tools for specific tasks, e.g.:
Beyond Compare for synchronising the XML files and images in the source folder and in the result folders
7-Zip to create Zip archives
curl for transferring results to REST endpoints
The more tools are involved, the greater the dependencies and the greater the risk of breaking changes with future updates of these tools – of which there were quite a few in that dozen years. It also makes it harder to run the batches from different machines. That is because it has to be ensured that each machine provides these specific tools in their specific version. XProc 3.0 offers the necessary functionalities out of the box, which provided the opportunity to significantly reduce dependencies by minimising the tools involved in the pipelines.