In my opinion the Japanese faction should be infantry focused with an added stealth element for ambush purposes and have the ability to cause massive rout to enemy infantry if played correctly.
Japanese Anti-Tank tactic consist of:
1. Destroying Tank with an Anti-Tank Gun.

"The Japanese 47mm gun can perforate the armor of an M4 in any range up to 800 yards." (Image: courtesy of Lovettartillery.)
2. Driving off its infantry with small arms and destroying the tank with hand carried explosives.

"The Conical Hand Mine (right) and the Experimental Hand-thrown Mine (left, quarter-section view) are antitank grenades that detonate on impact. They can penetrate 3/4 inch of armor." (Image: Lonesentry.com)
3. Immobilizing the Tank & destroying it later.
The Japanese used Satchel Charges to destroy tank tread and sprockets in order to immobilize it.
The Japanese might not have an effective Anti--Tank weapons, but they have an effective Anti-Tank strategies.
Source:
http://www.lonesentry.com/articles/jp_tankhunters/
http://mickmc.tripod.com/leavenworth-chapter3part3.pdf