Gimmicks like being immune to suppression will be inherently unbalanced (look at what happened to 'unique asymmetrical' OKW balance in CoH2 over time). There just isn't a good way I can see to balance banzai charge mechanics in a different way to 'Fire up!' and 'Sprint' abilities we've seen in the series.
At one end it would just 'feel' strange stalling for a prototype heavy tank as Japanese, for example and at the other end if they go light on the vehicle roster Japanese will just be a weak faction, period. The issue is that whatever you call that faction, it is no longer thematically 'Imperial Japan,' and whatever strategies they implement for them will not feel unique.
It's not that they couldn't make up an imaginary competitive vehicle roster for the Japanese, of which I think there is enough prototypes and low production runs to go around. However I don't think Relic will ever be able to successfully adapt the very different form of infantry-focused (semi-exclusive) island and jungle warfare that characterized that part of the conflict to the current CoH formula. I like the idea of an infantry-focused portrayal of the Pacific theater, which I feel is dominated by air war and naval war games currently.
