This is what I saw a company in smart metering do in this case, and it worked for them very well: They had all of the seniors on their own staff. Architects, T

This is what I saw a company in smart metering do in this case, and it worked for them very well: They had all of the seniors on their own staff. Architects, Tech Leads etc. They chose the tech stack, planned the development roadmap and in theory could've done it all themselves. Then they used contractors to build the actual code with their in-house seniors overseeing and advising (and doing some coding themselves) This way the essential knowledge was in-house, but they could vary the resources used for development depending on the need for new features.