I expect that if an existing loader were suitable, they could have used the ones from Linux, FreeBSD, or any of several other open source OSes.
However, this does raise the question of
why those weren't suitable, or more likely, why the principal (who may or may not be the OP - I'm guessing jmpf is speaking on someone else's behalf) wants a new implementation regardless of which existing ones might be suitable - the classic 'not invented here' problem.
The whole post is lacking details, in fact. We'd really need to know a lot more, starting with what it is for, what kind of restrictions there are, what the target system is, whether the result is going to be open-source or closed (politics aside, this has a bearing on how the project is approached and what tools could be used - which brings us back to the first point of this post), what development languages and tools are needed (for example, if you need it written in Rust and AVR assembly language, someone who doesn't know those won't be much help unless they are given the time to learn them), and the kind of budget the project has - not just 'how much will you pay us', but also 'what funds are available to support the project', which is kinda important even given the incredibly low non-salary overhead of software development compared to other kinds of engineering.
I realize that those details may not be available to the OP, or that the OP might not be free to discuss them, but it would help the prospective contractors to at least know ahead of time that the answers will require an NDA or something.
So, jmpf,
would you kindly tell us anything more you can about the project and what you/the principal need?