Have you looked at Japan's population profile? We're looking at 40 years of real hardship, starting right about now.
I quite agree that, in the long term, Japan should plan for a flat demographic curve, but the two baby booms of the 40s/50s and the 70s, followed by a plunging birth rate, mean the transition is going to be extremely painful.
> And maybe they can institute a program like Israel's to encourage Japanese nationals living overseas to return to Japan.
They did that in the 80s. The outcome did not reflect well on Japan.
In truth, Japan doesn't have an immigration policy. It has a managing foreigners policy, overseen the Ministry of Justice. Naturalization is permitted, but not encouraged. For instance, as a British Citizen, I'd have to officially make myself stateless before I could apply to naturalize.
Japan, as a nation, seriously needs to open its mind a bit if it wants to cope over the next 40 years. Either that, or start building grim, ultra-low-cost institutions to house its old folk.
Yes, immigration is problematic, but together with your second item, something could be worked by bringing the descendants of the Japanese immigrants, for example
And maybe they can institute a program like Israel's to encourage Japanese nationals living overseas to return to Japan.