There is a somewhat different possibility, viz. that even if M's
commitments are strictly inconsistent, some have a better claim to be
part of his considered view in the sense that they fit with more texts
that their rivals, fit more important passages than their rivals, or
cohere better with the totality of M's commitments. This sort of
Overall Fit need not conform with one's view about what view is right
or with M's own self-understanding.
Moreover, (a) has the limits that you suggest only if we are
philosophical relativists. Non-relativists will think that the
comparative plausibility of philosophical commitments could guide
choice (if only as a tie-breaker) among rival interpretations. Also,
I should say that even philosophical relativists might agree that the
interpreters background philosophical commitments can allow them to
see possible interpretations of texts that might otherwise be hard to
see, and so teach us all (even those without those commitments)
something about what the texts might stand for. Terry Irwin (no
philosophical relativist) has some very nice essays in the history of
ethics in which he shows how different philosophical commitments of
interpreters has played an important role in identifying and
adjudicating significant interpretive possibilities.
DB