Wait! If there was a sane set of APIs and data interchange formats that was standard across the whole system, development would be the simplest part.

It's because they have to shoehorn their solution into a morass of garbage software, that this turned into such a complex task.

The real answer is to dump ALL these huge contractors, and their 'solutions', and make something new and better, with proper engineers directing the process.

Imagine if Deloitte had been contracted to 'invent' the Internet...