I should add that the fact the Japanese train FO's in the left seat of the sim is just a quirk of the JCAB. You do not need to be trained in the left seat in your previous airline to have the P1 Command rating. You just can't have FO annotated on your licence like you would in Australia.
Having said all that when Ansett Airlines fell over a bunch of Ansett FO's paid for some sim time and did a P1 Command Rating Check with a CASA Checker, on what ever aircraft they were flying at the time in Australia to get a job in Japan.
So it's not impossible to get around the problem.