Probably these Japanese files such as included in BFBC2, BF1942 are not allowed to use in PR-mod due to copyright.
However that time will come sooner or later.
As Liam san says, people in Japanese PR community will help if the developing team for JSDF is recruiting volunteers for voice acting.
Of course I will help you but I have no skills/knowledges about modelling, programming and voice acting etc.
Please do not hesitate to order me if you need anything I can do(posting on JP PR community, asking question/researching for japanese ministry of defense

).