[GoNative]

Just because what you're suggesting makes complete logical sense doesn't mean that's how it is done in Japan.
I completely agree with you though. Certianly in Australia top executive positions in major companies are advertised worldwide seeking the best of the best. Many of the top positions in the biggest companies are held by non Australians because of this.
In Japan though there is still a pretty strong culture of promoting from within the company. Also top executives in Japan are paid only a fraction of what is normal in major international companies. CEO's at Japans 100 biggest companies only average something like $1.5 million dollars a year. The average in the top 100 companies in the US is nearly 10 times that. So even if Japan did seek out the best of the best for executive positions in their companies (which they don't) then I don't think there'd be all that many interested.