OK, here's what I believe is the sketch. It's been suggested that all co's become qualified in RH and LHS from the OCU. They seat swap during their tour and come up to captaincy needing only a short convex due their expertise. Theoretical advantages:
1. Gives co's credit for being capable pilots (contentious, possibly!) and enhances their credibility and confidence.
2. Double-co OCUs need run only half as frequently to meet co IPS figures. No stude capt, because they're on the short course. Half the OCUs = half the costs (simplistic, I know).
3. Less time in training world (possible disadvantage in today's micro fg hours climate - for some fleets) = more time in operational environment = better professional/career potential.
So, take aim. In your own time - carry on. Any CAA wallers know if 'capt in LHS only' could become air law in the future?
Z