My infrastructure partner brought me a blueprint for the systems we'd need going forward. Instead of hiring it out or waiting on a proposal cycle, I told him we'd build it in house first and then hand it back to him to try to break. Within days we had a secrets manager deployed, our project and CRM tools stood up, and our whole agent roster under review, on what I called at the time the biggest reboot we'd ever do.
My opinion on any consultant's design, technical or otherwise, is that the fastest way to actually understand it is to build it yourself before you hand it to the expert. If you wait for the proposal and then wait again for the build, you've spent weeks learning nothing. If you build it yourself first, you own the knowledge regardless of what the expert eventually tells you is wrong with it, and the handoff becomes a real adversarial review instead of a formality. Speed is the tell that you actually understood what you were building.