I can relate. I am now on a small team of half a dozen (2 front, two back, 2 devops). We've been smashing it for the last year, replaced a hodgepodge of systems with a configurable framework and a modular integration layer with third-party systems. As a reward our work the management are bringing in a consultancy we are supposed to train to replace us. That will be a very expensive and inefficient exercise. How do I know? Our small team was created to deliver what the previous consultancy could not do in 5+ years. That experience taught me once again that management in large organisations have no idea what they want to build, how to build it, how to maintain it, and that's where large consultancies come in, milk the client for all they can and leave a massive mess behind them.
The solution sounds simple: Refuse to train the incoming consultants. You can do this indirectly by quitting before the consultants arrive, or, directly, by telling mgmt that you refuse to train your replacements. Your experience sounds great to sell yourself into a new role with better managers.
