It sounds like what you'd like to do is to specify a URL in Central and have submission json sent to that endpoint every time a submission comes in, is that right? You can find a discussion on this kind of functionality in this thread.
As you've found and will see in the ideas thread I linked to, that's not something that Central can do currently. One of our major goals for Central is for it to run reliably on inexpensive hosting platforms with fast submission ingestion. This leads us to be very thoughtful about what we add to the platform and what we let other processes manage.
We've also learned from the Aggregate experience. Although many people like you found value in the JSON publisher, it was not very reliable and could fail in subtle ways. We want to make sure that if and when we take this kind of functionality on we can be confident about its reliability and completeness.
The thread I linked to above has some questions about your needs that would be helpful to get your answers to.