Seems to me both pointless and dangerous.

I don't see why the Japanese government would feel the need to get involved with other nations' troops. Seems like it would just open a can of worms for them. If it's because of North Korea, or to strengthen their position in the region, then the current deal they have with the U.S. involving military activities should be enough. I think Japan's current position in the international community is much more preferable: neutral in most outside conflicts, not much attention focused on them outside of their region. I'm unaware if Japan has ever been a target for terrorism, but making themselves more closely involved with the activities of more influential powers would definitely risk that.