One question. Assuming Japan starts feeling like they can "start tossing their weight around again," just where would they toss that weight to? Korea? I doubt they'd trade Pyongyang and Seoul for Tokyo. China? Yeah, right. That leaves the Philippines and Australia, and all the Japanese have to do is look at Hiroshima and Nagasaki to see what they'd get for screwing around that far south again.
How the hell would I know what a reinvigorated Japanese militarism would do? Maybe Taiwan! That was a Japanese possession. So were the northern islands of Japan, which the Russians still haven't returned. Or maybe they'd just take Guam or Saipan or Hawaii, which they own most of already?!?!?
I doubt they'd be particularly rational about it. From what I've seen, most Asian governments with a substantial military to toss around aren't particularly so.