I posted this on the other thread. But I don't want people to be distracted, so I'll put it in its own thread.
Japan has a very good military - a small sized military for a nation of Japan's size, but very good in quality. At the year 2007, though, several pressing needs demand to be addressed:
Offensive strike missiles. Long-range ballistic missiles, and cruise missiles fitted to submarines, could allow Tokyo to strike at North Korean targets. This would be useful in a pre-emptive scenario (i.e., North Korea has a nuke or bio/chem weapon on the launch pad ready to strike Osaka or Yokohama, etc.) $4 billion over five years.
New fighters Japan's fighter fleet is aging and getting outdated. The F-4s should have been replaced by now and the main fleet of 223 F-15Js is also over 20 years old. The Eurofighter Typhoon is currently the leading candidate to replace the F-4s, but what's going to replace the F-15s? We're talking around 250-300 fighters, which is a huge amount of money. $20 billion over eight years.
More missile defense. Japan right now has only two PAC-3 batteries around the Tokyo region. This is not enough. The government should try to get the licensing rights to co-produce PAC-3 with the USA, and to deploy more around all major cities, perhaps up to a dozen batteries. There should also be more spending on SM-3, and also more C4ISR and radars and comm/integration for the whole national missile defense shield as a whole entity. $9-11 billion over six years.
More submarines. The JMSDF has only 16 submarines. They are capable, but an insufficient number. Furthermore the time may come when Tokyo will need submarines with more capability and range for extended missions (re: UN peacekeeping commitments, energy security, etc.) and nuclear submarines may be called for. Japan should build 8 more Oyashio submarines and do research and development on SSNs. $16 billion over ten years.
P-8 Poseidon maritime patrol aircraft. Japan currently has a fleet of over 100+ P-3C Orion aircraft, built under license. These are getting very old and aging despite constant updates. Tokyo should try to either purchase outright, or get the license to build, the Boeing 737-based P-8 Poseidon antisubmarine aircraft. Anywhere between 40 and 70 planes are required to fill the JMSDF's antisubmarine aircraft requirement. $15-20 billion over ten years.