There are (solvable) problems with my original recommendation:

1. sys.implementation is by definition not suitable for third-party import hooks to modify
  + it is set during the Python implementation during runtime init
  + it is effectively read-only after that
2. "opt_levels" is too specific to the CPython status quo
  + there are other ways to encode the optimizations of a bytecode file [1]
  + "optimizations" would probably be more correct
  + that opens a whole can of worms (e.g. what does sys.flags.optimize mean)

So we may want to think this over a bit before going any further.  I'm going to collect my thoughts on this and write more later. :)


[1] In PEP 488 it says:

    It is expected that beyond Python's own two optimization levels,
    third-party code will use a hash of optimization names to specify
    the optimization level, e.g. hashlib.sha256(','.join(['no dead code',
    'const folding'])).hexdigest().