I might be ignorant, but wouldn't having our own ILogger interface with a PSR-3 compliant implementation be the best? As in implementing variable interpolation.
I only skimmed the MAY, MUST, SHOULD etc. but to me it sounds like the best solution.
Having an interface with a `$context` argument that isn't used in the implementation seems like the worst solution.
Well, it's late and I haven't read the code, so...