I want to do a similar change - have award itinerary booked SFO-NRT; HND-HIJ; CTS-NRT; NRT-SFO and just want to cancel the CTS-NRT leg. Agent said he had to cancel entire itinerary since it is rerouting, and all award seats would go back to inventory with low chance of rebooking to get the TPAC seats in J. Is there a way around this with a more competent agent?