JL719 (NRT-SIN departs at 10:55) and JL710 (SIN-NRT departs at 22:40) uses a 777-200ER with W51 configuration, which is a 3 class config (Y, PY, C) used for long-haul flights. PY cabin is used as Y on both flights. JAL opens up certain seats in the PY cabin for OW elites. But you probably won't make the JL719 connection though. That's one of the pros to fly on JL if your itinerary includes these two flights.

By the way, transpacific upgrades on JAL is only 10,000 JMB miles one way till end of March. If you have ways to get those miles, it's also another option.