Hopefully they will resume the 788 as soon as figure out a solution for the battery problems.
For the KUL-NRT route, JL flies their older 767 with a Skyrecliner on an overnight flight. I am thinking a short hop over to SIN on a MH flight, followed by a connection on a JL 788 with their NEO seats would be a more comfortable overnight flight experience from KUL to NRT. Otherwise the slanted lie-flat seats offered by MH seem like a reasonable alternative.