I don't doubt that KE could interline your bag to HA. They should be able to as they are partners! My problem was with Air China's failure to interline; my guess is that a lot of other Asian carriers to/from ICN would not do it either.

Perhaps HA could arrange with KE to check in bags earlier than the 3-hour window? The SkyTeam (Delta et al.) Alliance appeared to have such an arrangement.