The Aegis ships can't just be readily exported, because they have a lot of cutting edge American radars and weapons on them, so the USA itself would have to agree that the potential buyer is a trustable nation to sell it to. For example if Japan wanted to sell Thailand and Aegis ship I think the USA would oppose it, however if Japan wanted to sell an Aegis ship to Australia it would likely be allowed. As for other ships like the non Aegis ships that Japan has, like the Asahi class and the Mogami class, these have Japanese radar systems and weapons systems generally, so Japan could sell these to whoever they want. However it would still be wise for Japan to be careful about just selling Japan's own advanced indigenous equipment to just anyone. Japan should export 1 generation old equipment that is still more capable than equipment that the target nation has. It means building 10 fast missile boats for the Philippines and arming them with the Type 90 anti-ship missiles. Japan itself won't need these missiles anymore as it switches over to the type 17 missile. But the 200km range type 90 missile on board some fast missiles boats would give the Filipino navy a powerful capability, but also if somehow technical specs reached China it wouldn't matter as much.