This functionality is very useful. Can we add in an additional functionality?  There is an increasing need to support implementations of GMPEs (especially older ones) for which it is not possible to follow the high level quality assurance (i.e. verification against an independent code). It would be useful to add in a similar feature to raise a warning when such GMPEs are used.
For example:
if getattr(cls, 'non_verified', False):
    msg = '%s is not independently verified - the user is liable for their application' % (cls.__name__)
    warnings.warn(msg, UserWarning)