coming from this current situation you were also involved, I went ahead and tried to think about a way to cache a well known structure (of tokens) once and be able to create clones on demand in the fastest possible way.
Here there's a benchmark, and (not surprisingly) the result is that Function instrumented in a super-safe way, basically putting a stringified JSON in it and returning it each time, smokes any other standard solution ... plus, it's not less safer by any mean.
Like it is for any proposal, I don't feel like exploring this approach, but also I don't think it would be faster than any solutions explored in the mentioned benchmark. Surely not faster to initialize, also considering that's an async by design solution, hence it won't work on the fly for synchronous operations like I need to have/do in my case.