ICN is a fairly efficient airport. It is certainly not out of the question to get the bags and re-check them. It will require him to go through immigration, get his bags, and then go to the TG counter and check them. Honestly if he has enough time that might be worth trying as opposed to working with TG and *hoping* they say yes and then *hoping* again that they actually send an agent to get them off the carousel and get them onto the TG flight.