I'm writing this from my work desk without a) a chart in front of me or; b) any previous knowledge of the corridor so this may be a silly response, but:
i) I have always assumed (yes, that most dangerous of words!) that pilots follow some sort of 'keep right' rule (like line feature tracking) to minimise the chances of head-on approaches?
ii) Could some mini-quad/semicirc rule not be employed? eg. x000 ft on QNH in one direction and x500 in the other? I don't know if the ceiling of MSA make this impractical...
Hersh